Diesel, the diesel engine has proved to be extremely efficient and cost effective.* Diesel fuel is priced moderately higher than gasoline but diesel has a higher energy density, i.e. Therefore, diesel engines in automobiles provide higher mileage, making it an obvious choice for heavy-duty transportation and equipment. Diesel is heavier and oilier compared with gasoline, and has a boiling point higher than that of water.* And diesel engines are attracting greater attention due to higher efficiency and cost effectiveness. The distinction lies in the type of ignition.* While gasoline engines operate on spark ignition, diesel engines employ compression - ignition for igniting the fuel.