The oil filter helps remove contaminants from your car engine’s oil that can accumulate over time as the oil keeps your engine clean. Clean motor oil is important because if the oil were left unfiltered for a period of time, it could become saturated with tiny, hard particles. These particles could potentially wear surfaces in your engine. This dirty oil can wear the oil pump’s machined components and damage the bearing surfaces in the engine. The outside of the filter is a metal can with a sealing gasket that allows it to be tightly held against the engine’s mating surface.