 Unlike petrol, the flash point of a diesel fuel has no relation to its performance in an engine nor to its auto ignition qualities.Diesel engines, like other lean-burn (excess of oxygen in proportion to the fuel) forms of combustion, recombine the atmospheric oxygen (O2) and nitrogen (N2) into mono-nitrogen oxides and , collectively known as NOx, due to the high temperature and pressure.While naturally present in the atmosphere, their excess can contribute to smog and acid rain, as well as influence human health after reacting with ammonia, moisture, and other compounds.