Diesel fuel in general is any liquid
fuel used in
diesel engines, whose fuel ignition takes place, without spark, as a result of compression of the inlet air mixture and then injection of fuel. (
Glow plugs, grid heaters and heater blocks help achieve high temperatures for combustion during engine startup in cold weather.) Diesel engines have found broad use as a result of higher thermodynamic and thus fuel efficiencies. This is particularly noted where diesel engines are run at part-load; as their air supply is not throttled as in a
petrol engine, their efficiency still remains very high.