What Really Happens When You Take Your Car In for an Oil Change

An oil change is one of the most common jobs a car needs, but many drivers do not know what happens once the car is in the service bay. Motor1 explains that it is more than draining the old oil and pouring in new.

Why is it needed? Inside an engine, dozens of moving parts work under high heat and stress. Engine oil makes a thin film between the surfaces to reduce friction and wear. It also helps carry away heat, protects against rust and carries dirt toward the oil filter. But oil does not stay perfect forever. Heat cycles, leftovers from burning fuel, dirt and the slow loss of its additives all reduce how well it works. The filter catches many particles, but it has limits too and needs to be replaced on the maker's schedule. There is no single interval for every car. Short trips, extreme temperatures, towing and dusty roads can change how often a car needs service, and the owner's manual is the best place to start.

When you bring the car in, the mechanic first works out which oil and filter it needs, since engines use different oil thicknesses and specifications. The mechanic may also look at the mileage, service history, dashboard warnings and any signs of leaks, and may check fluid levels, tires, belts and hoses. Then the car is placed safely on a lift or raised with proper equipment. Some cars let the mechanic reach the drain plug from underneath, while others have panels that must be removed first, and some have the filter on top of the engine.

Next, the mechanic finds the drain plug, usually at the bottom of the oil pan, puts a container underneath and lets the used oil drain. The oil may be warm, because many shops drain it after the engine has run, which helps it flow, but it must be handled carefully to avoid burns. The drain plug and its sealing washer are checked, and the washer is replaced when needed.