What is the function of engine oil in a combustion engine?

Engine oil in a combustion engine serves multiple important functions. First, it provides wear protection by forming a thin film between moving parts, reducing friction and preventing metal-to-metal contact that causes damage. Second, it helps with cooling by carrying away heat from engine components, supplementing the cooling system. Third, engine oil has a cleaning function: it suspends and removes contaminants and combustion residues, keeping the engine clean and preventing sludge buildup. Together, these functions ensure the engine runs smoothly, efficiently, and lasts longer.