Directory:Acetone:Laws of Thermodynamics

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Acetone and the Laws of Thermodynamics

'Adjunct discussion / debate pertaining to the Directory:Acetone as a Fuel Additive index page.'



(The following was moved from the Directory:Acetone as a Fuel Additive on Dec. 31, 2005.)

Does a few ounces of acetone have 1/3 the potential energy of 10 gallons of gasoline? If not, this is a bunch of wishful thinking.

: RESPONSE: It's not what that acetone does by itself. It's purportedly what it does to the gasoline's surface tension, enabling a more complete, and hence efficient, burn. Also, the acetone is cleaning up the engine without impairing lubricity.

If it were to increase mileage by 10% to 30% as we hear, where would that energy come from? If acetone, or the above product, increased mileage by enabling the fuel to burn more completely, someone would be selling it as a surefire additive to easily pass the strict emissions test in CA, no?. Even if you could achieve complete oxidation of the fuel, wouldn’t it mean straight gasoline and diesel is burning so poorly that 10% to 30% of it is leaving the engine as unburned hydrocarbons to be able to account for the 15% to 30% mileage increases we hear about in both gas and diesel vehicles? In all these years there hasn’t been one oil company, engine manufacturer, government or university, in the entire world, that hasn’t stumbled upon this?

: RESPONSE: That is not what is being claimed here. The opening paragraph of this page states that improvements in mileage by the addition of acetone have been modest, in the range of 2 - 10%, and that some of that is likely to be due to cleaning of the engine.

The above still holds. 2 - 10% of the fuel does not leave the engine as unburned hydrocarbons. BTY read down this page and you'll find several claims for 10% to 30% - that IS what is being claimed (by some). Look at the charts below.


In a popular article quoted above, Mr. Louis Lapointe states that greater combustion efficiency is achieved through the lowering of surface tension of the fuel by the addition of acetone resulting in a significant increase in fuel economy and lower exhaust emissions. Many aftermarket fuel additive companies have claimed significant mileage increases through better combustion as well.

Both gasoline and diesel, comprised of non-polar hydrocarbons, already exhibit very low surface tension. C8, for example has a surface tension of [21.80 dyne-cm compared to water at 72 dyne-cm at 25 degrees centigrade.

As a liquid is heated there is a corresponding decrease in surface tension up to the point at which the liquid vaporizes. In a warm, well running engine, the fuel is in vapor phase during the combustion cycle leaving surface tension no part to play as surface tension pertains to liquids, not gasses. During the compression stroke of a direct injection diesel engine, the temperature of the intake air is typically in excess of 1000°F (from compression) before the fuel is injected at more than 20,000psi while, in gasoline engines, the fuel is vaporized before entering the cylinders. Needless to say, during the ignition process, the greatly increasing temperatures and resulting turbulence vaporize any fuel that may still be in atomized form. The bulk of the vaporized hydrocarbons that do not oxidize are generally in regions of the cylinder which tend to remain at temperatures too low to support combustion and in areas where the mixture is too lean for the vapor to ignite an example would be the space between the piston and cylinder wall just above the top compression ring. This amount of unburned fuel though is quite small, ranging from 1% to 2% in modern gas and diesel engines. Those that would say that fuel is still burning after leaving the cylinder need to remember that exhaust temperatures measured in the exhaust manifold run between 1000F to 1400F while running at full power when the exhaust is at it’s hottest. These temperatures are far below a gasoline or diesel flame (>3500). Combustion efficiency is affected to a far greater extent by the physics inherent in engine design than by chemistry.

Quoting Chevron Oil : “Combustion catalysts may be the most vigorously promoted diesel fuel aftermarket additive. However, the Southwest Research Institute, under the auspices of the U.S. Transportation Research Board, ran back-to-back tests of fuels with and without a variety of combustion catalysts. These tests showed that a catalyst usually made "almost no change in either fuel economy or exhaust soot levels." While some combustion catalysts can reduce emissions, it is not surprising that they don't have a measurable impact on fuel economy. To be effective in improving fuel economy, a catalyst must cause the engine to burn fuel more completely. But there is not much room for improvement. With unadditized fuel, diesel engine combustion efficiency is typically greater than 98%. Ongoing design improvements to reduce emissions are likely to make diesel engines even more efficient.?]Reference

Another Authority : “Incomplete burning of fuel is insignificant in modern cars. Fuel combustion today typically exceeds 98 percent.? -- John Heywood, Ph.D, professor of mechanical engineering at MIT and an authority on internal-combustion engines.

Using the above figures, if the addition of acetone (or any other additive) to the fuel was to produce even 100% combustion, with zero unburned hydrocarbon emissions (which it will not), we would only realize an additional 1% - 2% increase in thermal energy. The diesel engine is about 50% thermally efficient, with 50% of the energy of the fuel available to turn the engine while the other 50% is being shed primarily as heat from the radiator and exhaust. This would leave an increase of .5% to 1% of usable energy that could be applied to overcoming friction in transmission, wheels, radiator fan, etc. and increasing mileage. Assuming our mileage averaged 18mpg, we would realize 18mpg + .5% to 1% = 18.09mpg – 18.18mpg in theory with the practical amount a fraction of that. Assuming acetone addition would provide 100% combustion efficiency, (and there is no scientific evidence to support the assumption that it increases efficiency at all), and discounting loss to friction in drive train, etc., the resultant theoretical increase of less than 0.1mpg would be so negligible so as not to be measurable.

Statements such as “Most fuel molecules are sluggish with respect to their natural frequency. Acetone has an inherent molecular vibration that "stirs up" the fuel molecules, to break the surface tension? are pure pseudoscience and are not found in the nomenclature of chemistry.

As a recent study by Cummins Diesel demonstrates, fuel mileage can be affected up to 30% by driving habits alone. How many are expecting to see an increase in mileage after the addition of acetone? How much is this expectation affecting driving habits? And how many people are going to report it if they saw no increase and how many will become discouraged and just "forget the whole thing"? How do we account for the people that report a decrease? Because many reported at one time that the world was flat in their experience, didn't make it so. Surely there are people that are seeing an increase in mileage but we can't jump to the conclusion it is due to acetone. K at

NOTICE: Please post questions at the end of an article instead of the middle.

RESPONSE: If engines are so efficient, why do they need catalytic converters? Incomplete combustion is shown not only by the presence of unburned hydrocarbons but also by the other by-products such as carbon monoxide and nitrogen oxides.

K12719: Thank you for your question. With combustion efficency at 98% that still leaves 2%. When you multiply that 2% by the millions of gallons burned each day in the L.A. area alone, it quickly becomes self-evident why catalytic converters are in use. Nitrogen oxides are a result of the high temperatures and pressures within the cylinders generated during combustion with the nitrogen and oxygen forming them from the air, not the fuel. Some of the CO is a result of oxygen atoms being stripped from CO2 (a product of complete combustion) within the flame while much is a result of incomplete combustion. The principle components of the brown smog you see in the L.A. and Denver areas are the results of nitrogen oxides and their degradation products. To combat the formation of these oxides of nitrogen, some of the exhaust gases are cooled then recirculated through the cylinder for the purpose of lowering the temperatures with the result of less nitrogen oxides being formed. On the horrizon is a possible design to lower the combustion temperatures with hope of producing fewer emmisions called “Homogeneous Charge Compression Ignition?. (

HONDA CHAIRMAN TAKEO FUKUI: "Even the best internal-combustion engines still waste more than 80% of the energy created by burning gasoline." —Reported in Wall Street Journal July 25th, 2005

K12719: I believe Mr. Fukui was perhaps refering to cars and not specifically to engines. Gasoline engines are 20% to 30% thermally effcient while the newer diesels, e.g., the DuraMax manufactured for GM by Isuzu, are 50% efficient. (Jet engines are 30% to 50% thermally efficient.) Combustion efficiency is about 98% while thermal efficiency is about 30% for modern automobile engines. Of the 98% of the energy, in the chemical bonds of the fuel, from the combustion process, roughly 30% is realized at the flywheel. The rest is shed as heat from the radiator and exhaust and used in overcoming engine friction, etc. About 30% of the usable energy produced by the engine is used to overcome friction in the transmission, differential, wheel bearings and tires, leaving us about 20% of the energy of the fuel being used to move the car forward. This then would account for the 80% “wasted? that Mr. Fukui refered to though, I’m not sure that “wasted? would be my choice of words nor am I sure that is the term he acually used. The quote you refer to is a quote by Joseph White, a staff reporter of the Wall Street Journal and not a direct, or referenced, quote by Mr. Fukui himself. For an indepth view of the workings of the internal combustion engine, I would recommend “Internal Combustion Engine Fundamentals? by John Heywood, PhD, professor of mechanical engineering at MIT.


k12719{at} - Acetone additive skeptic, and primarily instigator of the above debate.

See also

Directory:Acetone as a Fuel Additive - directory

Acetone Discussion List

Directory:Fuel Efficiency directory index at PESWiki

- Directory







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