Your engine relies on motor oil to be able to run, and to disperse heat. The internal parts in your engine run on extremely close tolerances, between pistons and cylinder walls, bearings and journals and other moving parts. These clearances are tight enough to generate a lot of friction and heat – without the lubricating film of motor oil, engine parts would quickly overheat to a point where they fuse and weld to each other, seizing the engine.

The combustion process also produces incredible heat, with hundreds of thousands of tiny explosions that provide power and torque to get your vehicle down the road. The byproduct of those explosions is carbon, however, and as motor oil is doing its job, it becomes contaminated with carbon, acids and microscopic metal shavings, all of which are the byproducts of the combustion process.