Sulphur dioxide (SO₂) is not typically produced in petrol engines in significant amounts. Petrol engines primarily emit pollutants such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM) due to the combustion of petrol.

Diesel engines, on the other hand, release sulphur dioxide as a result of the higher sulphur content in diesel fuel. When diesel fuel is combusted, the sulphur present in the fuel reacts with oxygen to form sulphur dioxide. Sulphur dioxide is a harmful gas that can contribute to respiratory problems and other environmental impacts.

Petrol engines, which use petrol as fuel, have lower sulphur content compared to diesel fuel, and most modern vehicles are equipped with catalytic converters that help reduce the emission of pollutants. Petrol engines also operate at higher temperatures than diesel engines, which means more complete combustion of fuel, leading to fewer pollutants.