In the automotive industry, engine downsizing is the practice of utilizing smaller combustion engines over larger ones of the same power capacity when manufacturing vehicles. It is the result of car manufacturers attempting to provide more efficient vehicles that emit fewer emissions, often mandated by legislative standards. The term generally relates to traditional internal combustion engines powered by petrol or diesel.
Many manufacturers are reducing engine displacement and the number of cylinders. By adding a forced aspiration device (turbocharger or supercharger) and direct injection technology, they provide a powerful engine with similar performance to a much larger engine, but with much improved efficiency and reduced carbon emissions. A smaller engine is also often lighter, so less overall energy is expended while driving. Reducing the number of cylinders also reduces the amount of friction in the engine, increasing the efficiency.