diesel

Diesel is a petroleum derivative used for fuel and gets better fuel efficiency than gas, although as it combusts to produce the energy harnessed to drive engines, it has dirtier emissions than straight gas.

A vehicle, usually a truck or bus, which has a diesel engine and runs on diesel fuel is also referred to as "a diesel." Diesel engines are recognizable from gas engines in the distinctive noise they produce. Diesel engines are also different from standard engines in that they ignite fuel by compressing air in the cylinder to sufficiently high temperatures, rather than by an electric spark. Diesel engines are more efficient than standard gasoline ones, and therefore are utilized in cargo trucks and other large vehicles that drive long distances and/or carry heavy loads.