...that gasoline is a highly-flammable substance in the presence of an open spark, flame or incandescent surface. But consider this: The self-ignition temperature for gasoline, depending on how it is blended, is between 300 and 400 degrees Celsius. Diesel fuel and motor oil will self-ignite somewhat more easily, at approximately 200 degrees Celsius! This means that in the presence of heat alone -- without an open spark or flame -- spilled diesel fuel or motor oil will catch fire at a lower temperature than gasoline will.