Jim H,

You are comparing apples to oranges when comparing ignition points in the air and inside an engine. The flash point has to do with vaporization of the fuel in still air. Inside the engine, the Diesel fuel is vaporized by the injectors so the air flash point is not important. Diesel fuel actually explodes inside the cylinders more than Gasoline, thus the Diesel knock. Gasoline will also knock if it preignites before the spark if the octane rating in not high enough.

I read the Chevron article, and I can see nothing in it that contradicts any of my previous startements. As Chevron said, the higher the cetane number, the lower the ignition point of the fuel. Since gasoline has a much lower cetane number than Diesel fuel, a Diesel engine will be harded to start on gasoline. This is what the Chevron article related to.

The principel behind using high octane gasoline is to resist preignition in high compression spark ignition engines.

P E H