Why do car engines cause oxides of nitrogen to be produced?

Car engines produce oxides of nitrogen (NOx) primarily due to the high temperatures and pressures during combustion. At these conditions, nitrogen from the air reacts with oxygen, forming NOx compounds. Additionally, the presence of excess oxygen in fuel-rich combustion environments can further enhance the formation of these pollutants. NOx emissions contribute to air pollution and can lead to the formation of smog and acid rain.