Acetone In Fuel Said to Increase Mileage 15-35%

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.

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.” http://www.chevron.com/products/prodserv/fuels/bulletin/diesel/L1_toc_rf.htm]Reference

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 ~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 ~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 k12719@yahoo.com

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