Oil filters are cylindrical pressure filters positioned inline with the engine’s oil flow, typically mounted directly to the engine block. They remove ferrous particles, dirt, and combustion byproducts from lubricating oil, protecting critical engine components from wear. Construction utilizes a pleated cellulose or synthetic filter media, encapsulated within a metal canister. Anti-drainback valves prevent oil from flowing back into the sump upon engine shutdown, ensuring immediate lubrication at startup. Bypass valves allow oil flow even if the filter becomes heavily clogged, preventing oil starvation. Filter capacity and flow rate are critical specifications, varying by engine application and oil viscosity.