Has anyone tried this? It sounds like it should work quite nicely. Rubbing alcohol (isopropanol) is cheap and readily available. It is a very high octane fuel (octane rating approx 120), so shouldn't lead to detonation. Unlike ethanol/methanol, it is a secondary alcohol so has minimal corrosion concerns as it is a much weaker solvent and cannot be oxidized into acids, like the others. While many car manufacturers do not recommend (even if they will warrant their vehicles for use with higher concentrations) the use of ethanol concentrations of higher than 5%, much higher limits tend to be specified for IPA. While an oxygenate, it will lean out the mixture, but it is a weaker oxygenate than ethanol (IPA is 25% oxygen, eth is 33% oxygen and Meth is 50% oxygen), so can be added in larger quantities. Due to its high hydrogen content, and large bulk, it will also lower the total energy content and lower heating value of the fuel, lowering combustion chamber temperatures. Perhaps, additional cleaning could be obtained by adding water as an additional solvent. IPA has the property of making water completely miscible with gasoline, up to water levels of nearly 35%. The additional water in such a mixture, should further lower combustion temperatures, help to dissolve additional fuel system contaminants, clean valves, etc. I've heard of this tested once on an old lawnmower with a major carbon problem - tank was filled with 50% gas, 50% rubbing alcohol (70%). Ran fine, but perhaps not quite as powerful. At the end of the tank, the head came off, and it looked like someone had steam cleaned the engine. So, what do people reckon to my idea of sticking a gallon or 2 of 90% IPA into a half-tank of gas? Do you reckon this will do any good?