Volvo: gas vs. diesel, google search, air mixture

Question
i have a 1986 240dl, but this question is not about that car per se, however i think i have a question any decent mechanic could answer. which is: what is the difference between a gas engine vs. a diesel engine and why can't you put one type of fuel in the other type of engine? what would happen if the wrong fuel were to go in? is it possible to adjust a gas engine to receive diesel by changing the injectors or something. i don't know.
thanks, andrew

Answer
Gas and diesel are made from the same thing, petroleum based oil, but they have different properties.  Gas is more refined that diesel, they have different burn and flash temperatures, and general behave slightly differently and different engine pressures.  You can't burn either fuel in the opposite style engine because of fundamental differences with how fuel is burned in each.  Diesel engines are much higher compression, and rely on a "glow plug" rather than a spark plug to heat the super pressurized diesel/air mixture and ignite it, while lower compression gas engines rely on a combustion spark to ignite the engine.  There are numerous other differences that you could probably find  by doing a google search.  Bottom line though, is that you can't swap fuels because the engines are fundamentally different.  Diesel simply wouldn't burn in a gas engine.