One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them.
-J.R.R. Tolkien, "The Lord of the Rings" Trilogy
In Germany they call gasoline "Benzin", which is German for benzene. Back in 1998 and 1999 when I was first studying German tons of people went out of their way to tell me that, although gasoline is called Benzin in Germany, it does not actually have much, if any, benzene in it.
Rings with Tails
What is Gasoline?
What If Rings are Common?
While I was in Germany I once rented a Volkswagen Polo five door hatchback. It was the cheapest rental car available, and it had a five speed manual transmission and a 1.4 liter four cylinder EFI port injected engine. Power was not huge, but it seemed to have no difficulty cruising at what seemed like very high speeds to me on the Autobahn. There was plenty of power to cruise at 150kph (95mph) at 4,500RPM, although the engine sounded and felt horrible up above about 4,300RPM. The Polo would go even a bit faster than 95mph, but the noise and vibration from the engine just got worse and worse the higher it was revved above 4,300RPM. The 1999 through 2001 VW Polo 1.4 mpi base model eight valve engine is rated variously at 59hp at 4,700RPM or 74hp at 5,000RPM and the top speed for the five door Hatchback is listed as 160kph(99mph) and 172kph(107mph) respectively. This was a very slow car out on the Autobahn, most people were driving medium size Audis and going about 120mph, although there was also a trickle of trucking traffic and various slow drivers cruising at anywhere from 55 to about 70mph.
Traffic was generally not dense on the German Autobahns in the longer stretches, but then in and around cities and larger towns it was just regular freeway traffic with rather low posted speed limits of 100 or 110kph.
Back around the turn of the millennium the Germans seemed to generally be very opposed to the use of cars for routine commuting. Many of the richer working class Germans owned shinny new Audis that just sat in their garage, or even outside in a driveway day after day and week after week while they walked to the bus stop to get to work each day. The car was seen as an alternative to flying, and at that time in Germany the Autobahn system was actually the fastest way to get from one side of Germany to the other.
The main reason people owned cars was the freedom that it allowed. There are several aspects to this. What was most talked about was that a car was the easy and convenient way to travel longer distances for vacation or to visit family. The other very important thing though was having a ready alternative to public transportation. As long as the bus and light rail systems worked well people used them, but having a car in the garage was like a form of insurance. If public transportation became problematic for some reason the car was the alternative as opposed to walking being the alternative. For most poorer people in Germany walking was the alternative though, as even the cheapest little Fiats and Opels represented a large and significant expenditure. Many people in towns and cities did not own cars at all.
There were severe problems though. One was that car ownership created an elite class, and not owning a car was very pedestrian. I probably could have afforded to buy a small used car with the money I had while I lived in Germany, but I didn't have any tools with me or anywhere to work on it. People didn't service their cars in the street in Germany like I had always done back home. There were hobby mechanics who worked on their own cars, but they always kept everything neatly inside an attached garage. Most people who owned cars had all of the service and repair work done at dealerships and other high end auto repair facilities. Cars were much more reliable in Germany than in America. Still though I could not imagine having a car and being dependant on a commercial repair facility. That seemed very foreign to me.
The other problem was the fuel consumption. The cars in Germany seemed to be capable of much higher fuel mileage than those in America, but the results were elusive. The first person that I talked to about his car in Germany told me that he and his wife had been very disappointed to learn that their new Mercedes Smart Car was getting only about 35mpg, which he expressed as seven liters per hundred kilometers. That was not on the Autobahn, and it was not stuck in city traffic. That was running around small rural highways where the car was rated to do considerably better. I told him that I didn't believe the numbers he was quoting, that such a small car with such a small engine just would not be able to use that much gasoline under those conditions. When I rented the Polo 1.4 hatchback it also got only about 30 to 33mpg cruising at 35 to 50mph on small rural highways, which I absolutely could not believe. It was actually worse gas mileage than I had been getting from my 2144cc CIS mechanically port injected 1983 Audi back in California under similar driving conditions. And that was not even all that impressive of mileage from the CIS Audi. People were getting around 20mpg and even 22mpg on the highway from full size Chevy pickups with EFI 350 engines and four speed overdrive automatic transmissions. Something was obviously seriously wrong with these numbers.
The stable bond angle for a carbon to carbon bond is 112 or 113 degrees. This implies that the stable ring structure would be six carbon atoms bonded together to form a six sided ring structure. Six sided carbon rings have two forms, the benzene ring and the cyclohexane ring. The difference is in the distribution of bonds. Carbon takes four bonds, and in a hydrocarbon chain this means the carbon atoms are single bonded to each other with two hydrogen atoms on each carbon atom. A benzene ring (C6H6) is six carbon atoms with one hydrogen atom on each carbon atom, three carbon-carbon single bonds and three carbon-carbon double bonds. A cyclohexane ring (C6H12) on the other hand has two hydrogen atoms on each carbon atom and just single bonds between the carbon atoms.
The first and most important thing that jumps out is that it seems that both benzene and cyclohexane rings are much more common as part of a larger molecule as opposed to existing just on their own as benzene and cyclohexane. There are innumerable (not literally) compounds that have one, or even two benzene or cyclohexane rings in them.
The ring structures are significant because they have somewhat different combustion properties than hydrocarbon chains. And it is also significant that benzene rings and cyclohexane rings have rather different combustion properties from each other. The benzene ring has three of the stronger carbon-carbon double bonds, which is very significant. The main release of energy in burning hydro carbon fuels is the formation of the strong carbon-oxygen double bonds in carbon dioxide. The carbon-oxygen double bonds are dramatically stronger than the carbon-carbon single bonds, so the formation of carbon dioxide releases a large amount of energy. In a benzene ring each carbon atom already has one stronger double bond that has to be broken before carbon dioxide can be formed. This means that each molecule of carbon dioxide formed does not release as much heat when benzene is burned as compared to cyclohexane or carbon chains.
The main thing about the ring structures though is that they burn hotter. Just as long hydrocarbon chains burn hotter than short hydrocarbon chains the ring structures tend to burn hotter than short hydrocarbon chains. In cyclohexane the ratio of carbon to hydrogen is similar to long hydrocarbon chains. In benzene the ratio of carbon to hydrogen is of course much higher. This would mean that although benzene has a lower energy content per pound it is able to burn very hot.
Which is a more powerful motor vehicle fuel: Hotter burning benzene or the higher energy content cyclohexane? I don't have any numbers to go with these generalities here, so your guess is as good as mine. The other thing I don't know much about is the prevalence of these ring structures in crude oil and gasoline. What is obvious is that race gas is largely made up of ring structures. The ring structures not only burn hotter than short hydrocarbon chains, but the ring structures also require higher temperatures and pressures for compression ignition meaning they can be used in higher compression ratio gasoline engines. The ring structures would also tend to provide faster flame front travel speeds, as a ring tends to break down all at once as opposed to hydro carbon chains that gradually unravel from the ends. This all sounds very much like race gas. A hot burning, high pressure gasoline for high compression ratio engines that also has a rather high flame front travel speed.
The big question that remains though is as to the prevalence of these ring structures. Are compounds with benzene rings or cyclohexane rings present in significant quantities in crude oil? That I just don't know.
What I can say for sure though is that the larger the hydro carbon compound the less significant the ring structures would tend to be, at least in terms of the temperature of combustion potential of the fuel. If cyclohexane alone is compared to methane there is a dramatic difference. The hydrogen to carbon ratio in methane (CH4) is 33% on a mass basis. The hydrogen to carbon ratio in cyclohexane (C6H12) is 17% on a mass basis. A dramatic difference. If on the other hand cyclohexane alone is compared to straight hexane the difference is much less significant. The hydrogen to carbon ratio in straight hexane (C6H14) is 19%, very similar to cyclohexane. Methane has a whole lot less carbon in it than most combustion fuels. The hydrogen to carbon ratio of slightly longer hydrocarbon chains quickly gets much closer to that of cyclohexane. Even propane (C3H8) has a hydrogen to carbon ratio of 22.2% on a mass basis.
Somehow longer hydrocarbon chain fuels do appear to burn considerably hotter though. Butane (C4H10) has a hydrogen to carbon ratio of 20.8% by mass, but appears to burn a lot hotter than propane. Obviously there is more to the molecular physics of the temperature of combustion potential than hydrogen to carbon ratios alone. In the case of propane versus butane the dramatic difference in temperature of combustion potential likely has something to do with the difference between stripping off the endmost carbon atom versus stripping off the more centrally located carbon atoms. Propane has two endmost carbon atoms, and then only one centrally located carbon atom. Butane has twice as many centrally located carbon atoms, and that likely has something to do with the large observed difference in temperature of combustion potential between propane and butane.
Similarly it might be said that a cyclohexane molecule has six centrally located carbon atoms, and that may in some way explain a considerably higher temperature of combustion potential. I have seen some vague references to pure cyclohexane being used as race gas in four inch stroke length engines.
Benzene has a spectacularly lower hydrogen to carbon ratio of 8% on a mass basis, which would seem to indicate a much higher temperature of combustion potential. Does benzene burn significantly hotter than cyclohexane? I really don't know. What is clear though is that benzene would have a considerably lower energy density on a mass basis than cyclohexane.
Clearly either benzene or cyclohexane alone would be a rather high pressure fuel that could be run in very high compression ratio race engines. There are also molecules that might be found in crude oil or gasoline that have a benzene or cyclohexane group on one end of a hydrocarbon chain. These rings with tails would tend to require lower compression ratios. It would be sort of like mixing some gasoline in with pure cyclohexane, the fuel would pop off on late compression ignition at much lower temperature and pressure points.
Rings with tails would tend to be somewhat more powerful and hotter burning than hydrocarbon chains alone, but the difference might be rather small if it is long hydrocarbon chains that are being compared to rings with long tails. In other words ring structures would tend to be very significant for the temperature of combustion potential of gasoline, but a large concentration of ring structures in diesel oil wouldn't make as dramatic of a difference. The long hydrocarbon chains somewhat dwarf the unique combustion properties of the ring structures.
These rings with tails molecules might to something else seemingly unexpected also; they might actually have a slower flame front travel speed than either hydrocarbon chains alone or rings alone. The reason for this is that hydrocarbon chain unravels from both ends, where a ring with a tail starts unraveling just from the tail end. Only once a substantial portion of the fuel has burned does the ring finally break down and participate in combustion. This would tend to depress overall flame front travel speed of the fuel. Rings alone might have a higher flame front travel speed because they break down sort of all at once when the ring structure comes apart. Rings alone would be used in higher compression ratio engines, so the temperatures and pressures during flame front travel combustion would be substantially higher than in a lower compression ratio engine. The rings with tails molecules would need to be used in a lower compression ratio engine, or at least with less spark advance, so the temperatures and pressures during flame front travel combustion would be lower and the rings themselves might seem to be somewhat resistant to getting going and burning.
These rings with tails molecules would be considered a type of non-homogeneous fuel, and this would be true even if just one compound was isolated and run alone. The hydrocarbon chain, hydrocarbon chains, branched hydrocarbon chains or other molecular groups stuck onto a ring structure could have considerably different combustion properties than the ring structure itself. Even though it is a single molecule with a single name, it might have a decidedly dualistic set of combustion properties.
It seems to me that benzene or cyclohexane rings found in crude oil would likely be part of these larger molecules. Again though, the prevalence of rings alone versus rings with tails seems entirely unknown. Someone probably knows, but not me. It does seem likely that producing race gas is a process of isolating and refining the ring structures. This probably means isolating rings with tails, and then refining the rings with tails into rings alone or rings with very short tails by somehow striping off the additional molecular groups. Waste products from this refining process would likely be largely composed of methane, ethane, propane and other LPG fuels. Other solvents and light oils might also come off as waste products when refining race gas.
The ring structures themselves can also be synthesized, but that requires an input of energy which may dramatically reduce the overall refining efficiency.
Rings with long tails, with multiple long tails, or with long branching tails or other molecular groups stuck on probably would not tend to work as gasoline. Rings with one or two short tails made up of methyl groups, ethyl groups, propyl groups, butyl groups or even somewhat longer hydrocarbon chains might however work rather well as gasoline. The smaller the tail the more the combustion properties of the ring itself predominates.
Refining might also involve breaking down large molecules with a ring structure into rings with small tails and other petroleum products. A ring with a long tail that is too big to work as gasoline might be broken into pieces to form both a ring with a short tail that is highly desirable as a hot burning high pressure race gas style fuel as well as one or more shorter hydrocarbon chains that would work as either gasoline or LPG fuel.
There are also the napthalic molecules. The naphthalene group is two benzene rings which share two carbon atoms. At least some of the smaller napthalic molecules are rather light and volatile and might potentially be run in a gasoline engine. Other exotic compounds might also have interesting combustion properties, but the important point is that what is already present in crude oil dictates what can efficiently be made out of it.
And what about the folk legend of octane rings, does such a thing exist? Carbon atoms are capable of forming a smaller pentagonal ring structure, which squishes the carbon to carbon bond angle down to 108 degrees. This is very close to the stable 112 degree carbon-carbon bond angle, but it is bending the bond down to a narrower angle. The six sided rings appear to be more stable because the bond angle more easily stretches out than squishes down. The angles of a hexagon are 120 degrees, considerably more than the stable 112 degree carbon-carbon bond angle. The carbon atoms in a cyclohexane ring probably don't all lie exactly on the same plane, but are instead staggered to preserve something closer to the 112 degree stable carbon-carbon bond angle. The six carbon ring is a rather common structure because it is the smallest carbon ring structure that is able to preserve the stable 112 degree carbon-carbon bond angle. It does seem to me though that larger carbon ring structures might also form, and eight sided octane rings and nine sided nonane rings are in fact listed. I have however never heard much about the actual prevalence of eight and nine sided carbon ring structures, where six sided carbon rings are known to exist in a wide variety of forms. It seems that six sided ring structures are more stable, and probably much more prevalent. Solid information is again seemingly hard to come by. There is just that folk legend about octane rings in race gas, but it might just be a bunch of hot air.
What is clear is that anything hanging off of a cyclohexane ring is going to make for a weaker race gas. The most powerful, hottest burning, highest pressure race gas would tend to be just the rings themselves. Is it cyclohexane rings or benzene rings that are most powerful? I just really don't know. The only clue is that benzene has been immortalized in the German word for gasoline. Perhaps it really is benzene rings that make for the most powerful race gas. Or is that the Nuernburg ring?
What might make up the most powerful race gas is sort of interesting, but has only limited relevance to most normal uses of gasoline engines. The ring structures are more powerful, but what exactly does that mean for the irrationally large quantizes of gasoline being gulped down at gas stations? The first thing to keep in mind is that the traditional three and a half and four inch stroke length automotive and light truck gasoline engines demand hot burning gasoline. They will idle fine on any sort of gasoline, and with careful tuning some torque can be attained over narrow ranges of elevated engine speeds in late compression ignition mode. To get a four inch stroke length gasoline engine to run well though very hot burning fuel is required. It seems that the three and a half and four inch stroke length automotive engines were designed to run race gas. Does that mean that ring structures do in fact make up the bulk of crude oil? I think not.
What seems more likely is that isolated ring structures just became very popular at various times, and the petroleum companies were selling something very much like race gas as gasoline. There were times in the 1960's when some of the gas stations had as many as six different grades available, with six separate nozzles and hoses. At least one of those was often race gas. The main problem with this was that the very small price differences between the different grades led people to believe that the myriad of different types of gasoline were all similar in terms of refining efficiency. If one grade was able to deliver dramatically more power and cost about the same then this would seem to be the one that delivers the highest refining efficiency. Essentially the petroleum companies were tricking consumers into demanding expensive race gas, where what the consumers were actually demanding was the highest possible refining efficiency for gasoline.
Look out kid
It's somethin' you did
God knows when
But you're doin' it again...
And the pump don't work
'Cause the vandals took the handles.
Bob Dylan has admitted that his song lyrics were just childish rhymes that sounded good, but it is impossible not to read into things like that. Especially when nonsensical poetry is based on bits of folk wisdom and traditional story telling it can seem very compelling. If you pull out just the pieces that seem to most completely express an idea it is possible to use nonsensical poetry to support all sorts of ideas. The above lyrics are from a Bob Dylan song titled "Subterranean Homesick Blues", that name seems to even more thoroughly match a discussion of petroleum. More can be found also:
...admit that the waters
Around you have grown
And accept it that soon
You'll be drenched to the bone...
Come writers and critics
Who prophesize with your pen...
And don't speak too soon
For the wheel's still in spin
And there's no telling who that it's naming...
Come senators, congressmen
Please heed the call
Don't block up the hall
For he that gets hurt
Will be he who has stalled...
Your old road is rapidly aging
Please get out of the new one if you can't lend your hand...
The line it is drawn
The course it is case
The slowest now
Will later be fast
As the present now
Will later be past
The order is rapidly fading
And the first one now will later be last
Cause the times they are a-changing.
I don't think J.R.R. Tolkien was thinking at all about refining efficiency when he wrote "The Lord of the Rings", and I doubt that Bob Dylan had refining efficiency in mind when he wrote his coffee house jingles either. Both Tolkien and Bob Dylan certainly were conscious of how their expression of ideas would shape public opinion. Tolkien was an English teacher by trade, and Bob Dylan got his start singing other people's revolutionary social justice songs. What they both did though was just tell entertaining stories that neither made sense or had much factual content. They are entertaining stories, but in the end Tolkien and Dylan are both just entertainers. They weren't really saying much of anything other than "Hey, isn't this fun!" and "Large pay check please."
The credit for things that go well, and the blame for things that go wrong lies with those in positions of actual power. Those making informed decisions that affect the future. Consumers in general do often shape the future by "voting with dollars", but it is inappropriate to place much credit or blame on someone who is just buying what happens to work now or what they think for some reason is likely to work well in the future.
Squirrels have taken control of oak trees to a certain extent over millions of years by selecting for acorns that keep well when buried for storage. The squirrels have domesticated the oak trees, but it is impossible to blame any single squirrel for good or bad acorns. The squirrel itself knows nothing of evolution, adaptation, botany or agriculture. All the squirrel is doing is following the procedures that have been successful in the past. It might be possible to debate endlessly about what level of cognition, if any, a squirrel is capable of, but the fact remains that what squirrels have done to domesticate oak trees has been entirely by a slow process of evolving instinctual behavior.
The pressing question remains: What is gasoline supposed to be? It is very easy to argue that it shouldn't be at all, and this can be seen from several different perspectives. One is that gasoline is inherently less efficient in the refining process than diesel oil, so all internal combustion engines should use injection pumps and not spark plugs. This itself can be seen from several different perspectives. The obvious being that burning less petroleum is simply easier on the planet and the other being that in the long run it is better to make the most of the energy sources available to us.
Another perspective is that we shouldn't burn petroleum for road transportation at all, in which case there would be very little need for gasoline of any sort. These ideas all center around some related concepts. One is climate change; dramatically increased atmospheric carbon dioxide and methane levels have raised global average temperatures in the past 100 years and the polar ice caps are disappearing. It has been clear for 25 years that I know of that weather patterns will shift and sea levels will rise. The questions have been how much and how soon. In recent years it has been looking like a lot, and very soon. Preserving a large portion of the polar ice caps is a goal that humanity should take very seriously, and this requires dramatic reductions in petroleum use. Some amount of carbon dioxide emissions from petroleum use can be absorbed by the biosphere, and some increase in atmospheric carbon dioxide levels can be tolerated without the total loss of the polar ice caps. The more petroleum is burned though the steeper the increase in atmospheric carbon dioxide, and a steep spike in atmospheric carbon dioxide levels is what causes such dramatic climatic changes over a short period of time. Not burning petroleum at all is the best way to slow climate change, but just dramatically reducing petroleum use seems to be a realistic strategy to preserve a large portion of the polar ice caps.
Global warming is only one future concern though. Reducing petroleum consumption is also desirable for other reasons. Burning less petroleum generally means less pollution. Yes, gasoline can be made to burn very clean; but there are still nasty emissions. Just the high heat and pressure alone disturbs the atmosphere and generates toxic oxides of nitrogen emissions. Burning less petroleum also means less tire wear. All that rubber that wears off goes somewhere, so lower speeds and fewer miles driven does equate to a cleaner and healthier environment. Smaller and more efficient engines in lighter vehicles also means less energy consumption and less pollution from manufacturing. A smaller engine requires less metal to produce, and a better running engine lasts longer so fewer new ones need to be produced. All around it is desirable to use less petroleum, but life must go on. And that means the production of manufactured products and the use many forms of transportation. The only reasonable solution is to make better use of what is available.
Perhaps the best argument in favor of efficient and moderate use of petroleum involves the evolution of human thought. Concentrated energy sources, mechanization and technology in general allow a higher quality of life that in turn creates the conditions for more and better thought. The predicament of global warming, rising sea levels and ever increasing pressures on agricultural land and fisheries can easily look hopeless. Hopelessness though is predominantly a symptom of lack of creativity. Humanity does face large real challenges, and naked competition with the squirrels for acorns is not much of a solution. The only way out is up, so to speak. And up does mean better technology. Not only more efficient and more effective, but also easier to own. Disposable surface mount electronics designed to work poorly and fail quickly pushes us towards naked competition with the squirrels for acorns not towards sustainable development.
The ultimate up and out has of course been the dream of colonization of Mars, but that is really rather ridiculous. We are quite trapped on this planet by gravity and distance. It is not that it impossible to travel to mars, it is just that it is too far and takes too much fuel even to get into orbit. If mars is ever colonized by man it will be by rather small numbers of colonists who eventually establish a viable population over many generations. It is not that colonization of Mars is entirely out of the question, it is just that it is mostly unrelated to current physical challenges here on earth. But looking up, far up, does have psychological advantages. There has to be a frontier of some kind. Because any expansion of civilization off of this planet is so incredibly challenging and seemingly unlikely we need to buy time, lots of time. If civilization continues to exist then means of expansion will eventually be found, but when the barriers to expansion are so vast and so impenetrable then continued success here needs to be sustained well into the future.
Immediate solutions involve better use of what was previously considered inhospitable land, and that requires good use of technology. The key though is that it has to be sustainable. Not just an illusion of sustainability, but development that actually does preserve the natural ecosystems. First it was man over nature, but once man had run over much of nature that didn't work well anymore. Then it was nature over man, but that does not leave much room for continued development of civilization and evolution of human thought. The in-between vision that has been so illusive is the dualistic idea that continued development is desirable, but it absolutely must not be overly destructive.
What this all adds up to is the idea that moderate petroleum use may be highly desirable. Petroleum has been beneficial for mankind, and can perhaps continue to beneficial into the future as a bridge to better and more sustainable means of powering civilization. Burning less petroleum means that it can be used longer, and ultimately it is the long term sustainability that is so important. Blowing it all quickly and then being left with no ready source of energy is a backwards step. A step towards naked competition with the squirrels for acorns.
And blowing it all quickly does appear to be largely a global warming and pollution issue as opposed to a petroleum supply issue. There certainly isn't any immediate shortage of oxygen in the atmosphere. The reason that rising carbon dioxide levels in the atmosphere are so significant is that there isn't much to start with. The baseline atmospheric carbon dioxide level ten years ago, according to the Encyclopedia Britannica, was 0.038%. If the amount of carbon dioxide doubles to 0.076% that represents an extremely huge increase, but would correspond to a reduction in atmospheric oxygen levels from 20.95% to 20.87%. That is a very small change in atmospheric oxygen levels.
It is assumed that most of earth's atmospheric oxygen was generated by plant life. Plants breaking down water to form gaseous oxygen and hydro carbons. This implies that finding, extracting and burning 100% of the fossil fuel in the planet, something that obviously is not practical, would result in most of the atmospheric oxygen being used up. The implication is that there is a very large amount of petroleum down there somewhere. Much of it might be very difficult to get at, but there is a lot of it. So much of it that the concern is not a limited supply of petroleum or a limited supply of oxygen, but rather a limited capability of the planet to tolerate increased carbon dioxide levels.
Doubling the atmospheric carbon dioxide level from 0.038% to 0.076% would require that a very large amount of petroleum be burned. If it is assumed that the atmosphere drops off in density only moderately at three miles from sea level then there is approximately 9x10^19 cubic feet of atmosphere. To increase the carbon dioxide concentration of that amount of atmosphere from 0.038% to 0.076% would require burning about sixty trillion gallons of oil over a short period of time. That is enough oil to run 300 million cars 15,000 miles per year at 50mpg for 600 years. This assumes that the majority of the cars are burning diesel oil at 50mpg, and that the overall refining efficiency is substantially high. Reduced refining efficiency of course results in higher carbon dioxide emissions for the same 50mpg at the consumer level.
Burning that sixty trillion gallons of oil over 600 years would result in a smaller rise in atmospheric carbon dioxide levels. Burning the sixty trillion gallons of oil all at once would cause the atmospheric carbon dioxide levels to spike up from 0.038% to nearly 0.076%, but burning it over a 600 year period would provide quite a bit of time for increased plant growth to absorb significant portions of that amount of carbon dioxide. As atmospheric carbon dioxide levels increase plants grow faster and larger, at least in areas where sufficient water is available. The oceans also absorb carbon dioxide, and carbon dioxide is transferred from oceans to silt and mud on the sea floor. If the sixty trillion gallons of oil are burned more slowly over a longer period of time then there is more time for that carbon dioxide to be mitigated by increased plant growth. How much? I don't know, but it does happen.
Another long standing planetary problem is desertification. Cut all the trees down, the water table drops and nothing will grow. This is related to global warming because less forest and more desert means less absorption of carbon dioxide so less petroleum can safely be burned without losing the polar ice caps.
So, how much petroleum can safely be burned each year? The easy answer is less than has been being burned each year over the past 50 years. Global carbon dioxide levels are rising steeply, global average temperatures are rising, weather patterns are shifting and the ice is disappearing. We do need to do a better job of managing this planet we are all stuck on.
First and foremost gasoline needs to be produced with the highest practical refining efficiency and the lowest possible overall carbon dioxide emissions. The lowest possible overall carbon dioxide emissions means producing gasoline products that result in low carbon dioxide emissions from the extraction and refining of the fuel as well as low carbon dioxide emissions from the vehicles themselves. That means a compromise between refining efficiency and engine efficiency. High efficiency from the vehicle engines themselves does little good if the fuel burned is expensive specialty race gas that requires large extra quantities of petroleum and results in large extra carbon dioxide emissions. And on the flip side a slightly higher refining efficiency does no good at all if the resulting gasoline product is dramatically weaker, with a lower energy continent and a much lower temperature of combustion potential so that dramatically larger quantizes of the stuff are required to do the same job. It is the overall efficiency that is significant, or more precisely the overall carbon dioxide emissions.
In attaining the highest overall efficiency and the lowest overall carbon dioxide emissions there would tend to be a slight bias towards more energy dense fuels. Moving the fuel around requires expenditures of energy, vehicles with larger fuel tanks tend to be a bit less effective and higher energy density tends to promote higher combustion efficiency. For the temperature of combustion potential of the fuel a bias in one direction or the other is not quite so clear cut. It tends to be more of a philosophical decision than a simple technical decision.
In a way the temperature of combustion potential is similar to energy density. Hotter burning fuels can attain higher thermodynamic efficiency in engines, so the same job can be done with less fuel. There is however another perspective when it comes to the temperature of combustion potential, and that is engine size. Going slower requires a whole lot less power, but dramatically reduced engine loads result in very low efficiency. Going slower requires smaller engines, but there is a practical limit to how much stroke lengths can be reduced. A lower temperature of combustion potential allows lower mean piston speeds, which means engines can more easily be made very small. Smaller engines allow higher efficiency down to lower speeds, and going slow has the potential to save huge amounts of fuel. Increasing travel speed from 40mph to 80mph does not just double the power requirement, it more than quadruples the power requirement. If it is just wind resistance that is considered doubling the speed tends to require eight times as much power. That means that if 40mpg is possible at 80mph then slowing to 40mph should be able to deliver upwards of 150mpg with the same size vehicle. Getting the same efficiency at the lower 40mph speed does however require an engine that will run efficiently at the much lower power output level. That tends to mean a smaller engine. Reducing the cylinder count alone to reduce engine displacement is not necessarily a good idea, as a lower cylinder count tends to result in poor transmission efficiency. The only solution is an engine that is either more radically under square or operates at lower mean piston speeds.
The first thing that has to be kept in mind is that contemporary three and a half inch stroke length automotive engines operate at much too high of mean piston speeds when they are making strong power at 5,000 to 7,000RPM. Even on the hottest burning gasoline products that have ever been available reducing stroke lengths from three and a half inches down to two inches yields dramatic increases in efficiency. Regardless of the type of gasoline used the three and a half inch stroke length is dramatically too long.
Still though, there is a limit to how much the stroke length can be reduced without compromising efficiency. An engine with an excessively short stroke length needs to spin up too fast to attain ideal mean piston speeds to run efficiently under a full load, and that not only makes the engine harder to use but also inherently less efficient.
Getting the compression ratio and spark timing just right to run at the latest possible time of late compression ignition allows lower engine speeds and makes longer stroke length engines somewhat more practical, but there are severe limits to how well this can work also. First and foremost it is the simple fact that gasoline engines appear to actually run better at the earlier and easier to hit 5 degree ATDC time of late compression ignition up in the higher 6,000 to 8,000RPM range of engine speeds. Then there is also the simple fact that the latest possible time of late compression ignition is much more difficult to reliably attain. A two or three inch stroke length gasoline engine can appear to make torque fairly well in the 3,000 to 6,000RPM range of engine speeds at the latest possible time of late compression ignition when everything is working perfectly, but this falls apart extremely easily when any small thing goes wrong. Including with the gasoline supply. This is the main reason that so many people have simply given up on the latest possible time of late compression ignition and declared that gasoline engines will only work up above about 6,000RPM. The fact that gasoline engines do actually appear to work somewhat better at the earlier and easier hit time of late compression ignition also remains.
All of these things add up to the three and a half inch stroke length being extremely excessively long on any type of gasoline. That is the important point. When trying to decide how much stroke lengths should be reduced though the questions about what type of gasoline is best do come up. On what was considered normal gasoline in the 1990's and up through 2015 the three and a half inch stroke length was dramatically too long, but the gasoline was fairly hot burning and just going down to a two and a half inch or even three inch stroke length appeared to work quite well. On the much weaker and colder burning gasoline that has been common for much of the past two years though even shorter stroke lengths are required. On this much weaker gasoline even a two and a half inch stroke length is too long for good efficiency and three and a half inch stroke length engines run extremely poorly. The stroke length must be fairly well matched to the combustion properties of the gasoline to be used, but there certainly is a range of stroke lengths that will work well. On the hotter burning gasoline that was common in past decades the range appeared to be about two to three inches, and a three and a half inch stroke length automotive engine was just a bit too big to work well.
On the much weaker gasoline products that have recently become common the range of stroke lengths appears to be more like an inch and a half to two and a quarter inches and two and half inch stroke lengths are just a bit too long to work well.
Gasoline engines with even longer or even shorter stroke lengths can be made to sort of work, but the farther from the ideal stroke length you get the lower the efficiency will be and the more difficult the engine will be to get to work well enough for any particular application. When stroke lengths are a bit too long gasoline engines tend to get very harsh around 4,000 to 5,000RPM as well as down at 2,500 to 3,000RPM, tuning is tricky and efficiency stubbornly remains rather low at all engine speeds. When stroke lengths are dramatically too long gasoline engines get very whinny with surging poor power delivery and efficiency plummets.
When stroke lengths are a bit too short gasoline engines can get a bit harsh around 6,000 to 7,000RPM and also down at around 3,500RPM, but these problems can mostly be avoided with carful tuning while preserving high overall efficiency. When stroke lengths are dramatically too short the engine just has to be run way up at very high engine speeds under full loads where it is difficult to get it to flow well, large amounts of gear reduction are required and the maximum attainable efficiency is reduced. Very short stroke lengths do however tend to work well for reduced load efficiency, so erring on the short side tends to be more desirable than erring on the long side.
If very small four and six cylinder engines of around 300cc total displacement for pushing roomy four door sedans around at hyper efficient 25 to 35mph speeds are desired then the bias would tend to be towards the absolute highest refining efficiency and absolute lowest carbon dioxide emissions even if it means a somewhat lower temperature of combustion potential from the fuel.
If both sporting performance AND efficiency are desired then the bias most certainly is towards the hottest burning fuel that can also deliver high refining efficiency and low overall carbon dioxide emissions. If going somewhat fast with small and lightweight engines and small and compact fuel systems is the goal then hotter burning fuels are highly desirable, even if it means some modest reduction in overall efficiency.
Basically what it comes down to is that fast can be a goal in itself, but it does require that compromises be made. Specifically less miles traveled. And by fast I mean cruising speeds up in the 45 to 55mph neighborhood. Cruising at 70 and 80mph is patently insane when fuel consumption and carbon dioxide emissions are considered. The only road vehicle that is at all efficient cruising at 70 and 80mph is an 80,000 pound gross vehicle weight over the road truck. Cars, small trucks and motorcycles are spectacularly thirsty gas guzzlers at those sorts of dramatically elevated speeds.
Just how these two alternate goals of very slow and very low fuel use or somewhat faster with somewhat lower miles per gallon relate to the actual compounds present in crude oil is not entirely clear. What is crystal clear though is that any gasoline product that has a lower temperature of combustion potential without a substantial overall increase in refining efficiency is wasteful and actually increases carbon dioxide emissions. A low temperature of combustion potential is not in itself a desirable property. A somewhat lower temperature of combustion potential can be well tolerated for very slow travel if it delivers a substantial boost in refining efficiency and lower overall carbon dioxide emissions, but the lower temperature of combustion potential itself can never be seen as desirable in any way. The reason that the low temperature of combustion potential is not itself desirable is the peak thermodynamic efficiency is inevitably lower for lower temperature of combustion potential fuels. Somewhat lower peak thermodynamic efficiency is just fine if it means higher overall efficiency and lower carbon dioxide emissions. If the lower temperature of combustion potential fuel and corresponding lower thermodynamic efficiency results in lower overall efficiency and higher carbon dioxide emissions then that fuel is barking up the wrong tree so to speak.
Potential candidates for gasoline compounds would fall into two categories. Those that have potential to deliver a good compromise between refining efficiency and performance with low overall carbon dioxide emissions; and those that don't. Outliers could be at a variety of extremes. Making ethanol out of petroleum would be a good example of an extreme outlier. Poor performance, low energy density, low temperature of combustion potential, low refining efficiency and high carbon dioxide emissions. Another outlier would be specialty race gas that delivers absolute maximum performance, but requires large quantities of petroleum. Some small quantity of ethanol might come off in normal refining processes, but trying to make more of it is insane. Likewise it is possible to get some quantity of the best race gas during normal refining processes, but trying to make more of it is probably not a good idea.
Other outliers might be certain oily slow flame front travel speed compounds that although they can be run in a gasoline engine cause too large of spark plug fouling and starting problems to be able to be considered real gasoline. Large quantities of these in-between gasoline and diesel oil compounds might tend to come off in the refining process, but they are best either mixed into diesel oil to prevent freezing in the winter or used in dual fuel engines that can be started on real gasoline from a separate tank.
The lightest and fastest flame front travel speed premium gasoline might also be considered something of an outlier, having such a fast flame front travel speed and popping off so easily on late compression ignition that it would have to be run in extremely low compression ratio engines. Very high flame front travel speeds and very low compression ratios can however be considered somewhat desirable because they make it easy to get gasoline engines to run well over wide ranges of engine speeds. The fast flame front travel speed is obviously a big advantage when it is difficult to precisely control when late compression ignition will occur. Popping off easily on late compression ignition can also be considered desirable from some perspectives. Higher compression ratios do contribute to better flow and higher thermodynamic efficiency, but lower compression ratios in gasoline engines have their advantages also. One is that it is actually possible to hit later times of late compression ignition with lower compression ratios, meaning that slightly lower minimum engine speeds can be used with the same temperature of combustion potential gasoline and the same stroke length. The pressure in the combustion chamber tends to change more abruptly as the piston rises and falls with a higher compression ratio. A lower compression ratio yields a less abrupt change in pressure, meaning that the time of late compression ignition can be stretched around a bit later at low engine speeds. A later time of compression ignition is not necessarily needed considering that gasoline engines actually appear to work better and attain higher peak efficiency at the earlier and easier to hit 5 degree ATDC time of late compression ignition versus the 15 or 20 degree ATDC latest possible time of late compression ignition. Still though stretching the time of late compression ignition around as late as possible to get the engine speed down a bit lower without harshness can be considered desirable in some types of casual cruising gasoline engines.
What it really comes down to is that fast flame front travel speeds and low compression ratios can easily be considered desirable, as long as it doesn't come at the expense of reasonable efficiency. If the temperature of combustion potential of the outlying super low pressure premium gasoline is so dramatically low that it requires much shorter stroke lengths than normal efficient gasoline then it has to be considered a specialty fuel.
It would be perfectly reasonable for an outlying super low pressure premium gasoline to be sold from a separate tank as a premium fuel. If however a regular gasoline with a much higher temperature of combustion potential AND a higher refining efficiency for overall dramatically lower carbon dioxide emissions can be produced then that is what MUST be available as regular gasoline. An outlying premium gasoline is not appropriate for use as regular gasoline just like an outlying specialty race gas is not appropriate for use as regular gasoline.
Hear me talkin commonwealth
In the commonwealth
But it's much to wealthy for me
Much too common for me
It's much too common for me
I angled down Australia and New Zealand too
I hurried up to Pakistan and India too
I came back to West Indies and had a cricket match...
Well, I would join the common market
But it's much too common for me...
There is a possibility though that the prevalence of ring structures in crude oil is so high that some grade of normal gasoline would be composed largely of those ring structures. I don't know if this is true or not, but I certainly can't rule it out at this point. If this is the case then gasoline distribution would be considerably complicated, and at least three grades of gasoline would be required. Cheap regular with a rather slow flame front travel speed and a somewhat lower temperature of combustion potential for use in very small engines would be one of the grades. There would then be two grades of premium gasoline. One would be predominately the ring structures and would deliver higher temperature of combustion potentials with a rather high flame front travel speed to be used in high output engines. The other grade of premium would be the super low pressure premium for use in very low compression ratio engines.
Mixing two of the three grades together might also be considered desirable for some applications. Performance and efficiency would tend to be highest when using just one grade alone, but mixing could do some interesting things. Mixing the hot burning premium about half and half with the slower flame front travel speed regular could deliver broad strong torque with a fixed spark timing value in smallish engines. Mixing 20% of the super low pressure premium with 80% hot burning premium would allow bigger power output and higher mean piston speeds from very low compression ratio engines. Mixing the super low pressure premium with the slower flame front travel speed regular or mixing all three together wouldn't accomplish much of anything useful, but might still be considered desirable for fine tuning of an existing engine. Add super low pressure premium until the compression ratio isn't too low, add regular until the flame front travel speed isn't too fast for the existing advance curve and try to get as much of the hot burning premium in as possible to boost power output.
Somehow though I suspect that the ring structures are not all that common, at least not common enough that they would tend to be available at the same price point. Even if approximately one third of a refining efficient gasoline stream was ring structures and/or rings with small tails these ring structures would tend to be worth quite a bit more. The price of the predominantly ring based grade of gasoline would be higher at least in proportion to the higher temperature of combustion potential. A 30% higher temperature of combustion potential gasoline would sell for at least 30% more simply because a 30% higher temperature of combustion potential could deliver a boost in efficiency sufficient to bring the cost per mile down on par with the cheaper lower temperature of combustion potential grade of gasoline. In reality a hotter burning grade of gasoline would tend to be worth even somewhat more that it's proportionally higher temperature of combustion potential based on it's high performance potential. For some applications hotter burning fuel and higher mean piston speeds simply means better performance. More power to higher mean piston speeds with higher thermodynamic efficiency is hard to argue with as desirable if it can be had at the same price.
What this line of reasoning means is that even if a substantial portion of the gasoline stream, up to perhaps as much as half, is made up of rings the ring based premium gasoline is going to tend to sell for substantially more per gallon than other grades of gasoline. This is sounding an awful lot like race gas as opposed to one of the grades of normal gasoline. If even just one fifth of the gasoline stream is made up of rings though the 2.5 to 4 times higher price of race gas versus pump gas is irrationally high. Rings making up one fifth to one third of the gasoline stream and having a 30 to 50% higher temperature of combustion potential would tend to sell for about 40 to 60% more per gallon. Not 250% or even 400% more per gallon as has been the case with race gas in five gallon drums. The 250% to 400% higher price per gallon of race gas seems to indicate a much smaller supply, perhaps as little as just 1 or 2% of the gasoline stream.
The 250 to 400% price premium for race gas seems to indicate the synthesis of ring structures in larger quantities than just come off of the gasoline stream as one of the petroleum products. Prices and economics can however be extremely muddled for a variety of reasons. The fact that the temperature of combustion potential of the gasoline has recently so dramatically shifted seems to indicate a somewhat higher prevalence of ring structures. If it was a predominance of ring structures that was yielding the substantially higher temperature of combustion potential of all grades of gasoline in recent decades then this seems to indicate that ring structures are in fact rather common in crude oil. How else could such hot burning gasoline have been so widely available at low price points?
The other possibility is much more sinister; that the currently very low temperature of combustion potential gasoline is actually an expensive specialty product that is resulting in higher petroleum use and higher carbon dioxide emissions and is only cheap because people won't pay more for such garbage. That is what it sort of looks like immediately after an abrupt shift from 20 years of dramatically hotter burning AND higher energy density AND rather fast flame front travel speed gasoline at the pumps.
The most important clue seems to be that the pumps that are labeled as selling gasoline with "Up to 10% Ethanol" were in late 2016 actually dispensing a motor vehicle fuel that smelled like and ran like gasoline mixed with 30 or 40% ethanol. It seemed to me like the petroleum companies were intentionally reducing the energy density of gasoline at their expense. Ethanol is much more expensive than gasoline, so mixing in 30 or 40% ethanol and selling the resulting fuel for less per gallon than gasoline was selling for a few months earlier seems like very poor business sense. Again though, prices and economics can easily go very wacky for all sorts of obscure reasons.
Now in the early months of 2017 somewhat more powerful gasoline that does not seem like it has ethanol in it has again been coming out of the pumps as 91 (RON+MON)/2 octane rating premium, but I still don't know what to think of the dramatic shifts in combustion properties that I have been seeing from month to month. Very annoyingly the somewhat more normal gasoline has been disappearing overnight.
At least my 9.7:1 386 stroker motor has been running crisply with just 21 degree BTDC spark timing both on gasoline straight from the pumps and on gasoline that has sat unattended overnight. The very low pressure gasoline is great for the lower compression ratio engines. I had sort of written off the 9.7:1 386 stroker motor when it was requiring 29 to 33 degree BTDC spark timing back in 2015 and early 2016 as the torque was very narrow from just 6,000 to 8,000RPM and the low compression ratio engine was very loud and seemingly very weak compared to running the same gasoline in the 11:1 hot rod 610 motor.
On this very low pressure gasoline there is no problem with the 9.7:1 compression ratio being too low. The 9.7:1 386 stroker motor has been running extremely crisply with 19 to 23 degree BTDC spark timing and torque and power everywhere from 3,000 to 9,000RPM are roughly proportional to the stock 10.2:1 610 motors as expected from the displacements and stroke lengths on the same gasoline. The 610 motors of course do a bit better than the little 386 stroker motor down low at 2,500 to 3,000RPM on this very weak low temperature of combustion potential gasoline and when the flame front travel speed is very high the larger bore 610 motors also do a bit better in the 3,500 to 5,000RPM range of engine speeds. The weak and low temperature of combustion potential gasoline tends to produce an abrupt power hit at 5,000RPM followed by narrow and surging difficult to control power to 6,500RPM in just about all gasoline engines. Interestingly this abrupt 5,000RPM hit can sometimes be even worse on the smaller bore 386 stroker motor on the same gasoline.
The abrupt hit at 5,000RPM was of course worse when I had the cam timing retarded four degrees. Going back to stock cam timing smoothed out the power delivery from 4,000 to 6,000RPM considerably on the same gasoline the day I did the project. Even with the stock cam timing though weak gasoline has been bringing back that abrupt hit at 5,000RPM followed by low power output above 6,500RPM. This has been true on both the 386 stroker motor and the lower compression ratio 610 motors.
The hot rod 12.2:1 610 motor tends to run a bit differently. With just 17 degree BTDC spark timing the power builds gradually and a bit harshly up to 5,700 or 6,000RPM and then takes off and blasts a fairly big pull all the way up to 8,000RPM. The 12.2:1 hot rod 610 motor with the dramatically lightened 332g piston running small amounts of spark advance tends to make seemingly irrationally large amounts of power to 8,000RPM even on very weak gasoline. When I swap gasoline back and forth I am constantly amazed at how that thing can pull so much harder at 6,000 to 8,000RPM than a seemingly nearly identical 610 motor running more spark advance. Even when it is extremely low pressure gasoline that requires only 17 degree BTDC spark timing in the 12.2:1 hot rod 610 motor. When it is extremely high pressure gasoline that is preventing the low compression ratio motor from making torque the difference is mostly down in the 3,000 to 6,000RPM range of engine speeds. Back in 2015 I saw that a lot. The stock 10.2:1 610 motor running 28 to 31 degree BTDC spark timing was just super harsh everywhere bellow 5,000RPM and made power only over a narrow range of engine speeds up to 7,500 or 8,000RPM. Then I would swap the same gasoline into the 11:1 hot rod 610 motor and the thing would just go ballistic everywhere from 3,500 to 8,500RPM with dramatically more torque than the 10.2:1 motor. And that gasoline was coming out of the pumps all the time.
In 2017 though what has been most annoying is that the gasoline just disappears. I go to the gas station and get some 91 (RON+MON)/2 octane rating premium gasoline and it sort of works in the 9.7:1 386 stroker motor. A bit of a surging feeling around 5,500 and 6,000RPM and not quite as much top end yank as was normal but fairly good power to 8,900RPM and all around reasonably good performance with smooth 100% reliable instant torque everywhere from 3,500RPM up. Then the next morning I fire the 386 stroker motor up, ostensibly on the same gasoline still in the same tank, and the power is just totally gone. Worse surging from 4,500 to 6,000RPM and then totally flat and lifeless above 7,000RPM and it won't rev past 8,000RPM at all. The obvious sign that it is dramatically weaker gasoline is the combination of nonexistent top end power with worse surging and a more abrupt hit at 5,000RPM. And the torque was even noticeably lower all the way down to 3,500 and 3,000RPM. It is one thing to get somewhat weaker than normal gasoline at the gas station, but then to have it replaced with even weaker gasoline over night is very frustrating.