What Causes Engine Oil to Turn Black?

[DeAna]

Engine oil turns black due to carbon deposits and oxidation products inside the engine, which indicates the oil is performing its cleaning function. Here is an introduction to the functions of engine oil: Lubrication: The primary role of engine oil is to lubricate the engine's pistons, bearings, and other components, providing protection. Sealing: When the engine is coated with oil, it creates a seal during the "power stroke," preventing high-temperature and high-pressure gases in the combustion chamber from leaking into the crankcase through gaps. Cleaning: Impurities and metal wear particles generated during engine operation are filtered out by the oil filter, keeping the lubrication system clean.