Thinking About Diesel

What are the differences between diesel and gasoline engines? Can these differences help us save on gas? Well, first of all, diesel engines have a higher thermodynamic efficiency. When they burn fuel, they convert a higher percentage of the energy available to useful work. Basically, all else being equal, they get more miles per gallon. However, to get these high efficiencies, they run at very high compression pressures. Because of this they need to be built strong, which makes them heavier. They are also more expensive to manufacture because of the strength requirements. Another feature is that diesels don't need electrical ignition systems, because the compression pressure is enough to cause the ignition. They need complex fuel injection systems though.

One interesting feature of diesels is that they can run on very low quality fuels. Even vegetable oil is enough to run them on. Try that with a gasoline powered car engine!