What does oil do in your vehicle's engine? If you answered "lubricate"; you're only partially right. While oil is primarily a lubricant, it also performs a number of other functions that are vital to the life and performance of your engine.
In addition to being a lubricant, oil also dissipates heat and makes parts run cooler; it helps reduce engine noise; it combats rust and corrosion of metal surfaces; it acts as a seal for pistons, rings, and cylinder walls; it combines with the oil filter to remove foreign substances from the engine.
When combustion occurs, temperatures can reach 2000–3000°F. (1093–1648°C), while pistons can easily reach a temperature of 1000°F (537°C). The high heat load travels down the connecting rods to the bearings. Both tin and lead are commonly used in bearings and become very soft around 350°F (177°C).
Oil in the crankcase can reach 250°F (121°C) after warm-up and is supplied to the bearings at these temperatures.
As the oil circulates, it picks up heat, and may be 50°F (10°C) hotter than the crankcase oil. Flow and circulation of the oil keeps the bearings at a safe heat level and is essential to limiting bearing temperatures. A continuous circulation of large quantities of oil is essential to long engine life.