Engine Oil Change: How to Do It Yourself

An oil change is the maintenance job with the best return on learning time. It takes forty-five minutes the first time and twenty-five once you have done it twice. The parts cost about twenty to forty pounds depending on the car, against sixty to one hundred and twenty pounds at a quick-fit centre. More usefully, doing it yourself means you see the oil that comes out, you know the filter got changed, and you know the correct grade went back in. None of those things are guaranteed when you drive through a service centre.

What you need before you start

Find the correct oil specification for your car before you buy anything. This is not optional. Modern engines have tight tolerances on oil viscosity and additive packages, and using the wrong grade causes measurable wear. The specification is in the owner's manual and usually on a sticker inside the oil filler cap or door jamb. It will look something like 5W-30 with an ACEA or API rating. Common specifications are 5W-30 for most modern petrol engines, 5W-40 for some turbocharged and older engines, and 0W-20 for newer fuel-economy-focused engines. Using 5W-40 in an engine specced for 0W-20 is not fine.

You will need the oil itself, a new oil filter, a new sump plug washer if your car uses a crush washer (most do), an oil drain pan, a socket or spanner for the sump plug, an oil filter removal tool for the correct size and type, disposable gloves, and a few rags. Have the correct quantity of fresh oil ready: the owner's manual gives the capacity for a drain and refill, which is slightly less than the total system capacity. For most hatchbacks this is four to five litres.

Draining the oil

Run the engine for five minutes before draining. Warm oil drains faster and carries more of the suspended particulates out with it. Do not drain from an engine that has just been driven hard: the oil and exhaust components are hot enough to burn.

Position your drain pan under the sump plug, which is a bolt at the lowest point of the oil sump, usually at the back of the engine. Loosen the sump plug with the correct socket: most are seventeen or nineteen millimetre, but some are hex or Torx. Once it is loose, unscrew it by hand and be ready to move your hand quickly as the oil begins to flow. Used oil at drain temperature is hot enough to cause discomfort if it flows over your hand, so position the pan well forward of the plug and then move the plug clear quickly as it comes free.

While the oil is draining, remove the oil filter. On most cars this is a spin-on canister on the side of the engine block. Use an oil filter removal tool: trying to remove it by hand usually fails unless it was fitted lightly. Have a rag under it as it comes off: there is always oil in the filter. Wipe the filter mounting surface clean and check the old filter seal came off with the filter. A second seal left on the block, with a new filter pressed over it, will cause an oil leak and an alarm within miles.

Refitting and filling

Fit the new sump plug with a new washer. Crush washers are single-use and the old one will not seal reliably even if it looks intact. The torque for the sump plug is in the service data, but as a practical guide, nip it up firmly and then give it a further quarter turn. Over-tightening strips the thread in the sump, which is an aluminium casting on most modern cars, and re-tapping or fitting a repair insert is a complication you do not want.

Before fitting the new oil filter, apply a thin film of fresh oil to the rubber seal on the filter. This helps the seal seat evenly and makes the filter easier to remove at the next change. Tighten the filter by hand only, firmly, until the seal makes contact with the block, then add three quarters of a turn. No more. A filter tightened with a tool will be impossible to remove by hand next time.

Pour in approximately half a litre less than the full capacity. Check the dipstick. Add in increments until you reach the maximum mark. Do not overfill: oil above the maximum mark aerates when it contacts the crankshaft, which reduces its lubricating properties.

Start the engine and watch the oil pressure warning light. It should extinguish within three seconds. If it stays on for more than five seconds, stop the engine and investigate. The light staying on after an oil change usually means the filter was not primed, the drain plug was not fully tightened, or the wrong grade was used. Check for leaks around the filter and sump plug immediately.

See the maintenance category for scheduled service intervals and what else to check at an oil change, and the parts guide for how to choose an oil filter brand.

What to Check While the Car Is Raised

An oil change gets the car in the air, which is an opportunity that most home mechanics underuse. While the sump plug is draining and you have ten minutes to spare, look around at what is accessible. Check the condition of the rubber boots on the driveshaft CV joints: cracks or splits in these boots allow grease to escape and water and dirt to get in, and a split boot caught early costs fifteen pounds and an hour of work, while a worn CV joint costs significantly more. Run your eye along the brake lines and fuel lines where they are visible from below. Any signs of corrosion, kinking or chafing are worth noting.

The underside of a car tells you things that are invisible from above. Rust on the sills, on the floor sections, or on the subframe mounting points is structural information. A wet patch on the gearbox or differential casing tells you a seal is weeping. Oil residue on the outside of the sump below the sump plug tells you the plug was either loose or the washer was not changed last time. Catching these things while the car is already up is the simplest form of preventive maintenance: the car is already raised, the work takes two minutes, and what you find will either reassure you or give you something specific to address before it becomes a problem.