Why do engines need oil? To clean, cool and lubricate the engine's moving parts. Oil can also help stop corrosion and sludgy deposits from building up. If your engine didn't have any oil, it would soon get stuck as the friction in the engine would mean it would overheat and become damaged. It needs changing from time to time as it degrades but between changes make sure you have the right level of oil to keep the engine working properly.
Why do I need to check the oil? If you only decide to do one check yourself, make it the oil. Engines that run smoothly still use a bit of oil so do check up between changes. Once a month should be fine. The oil pressure warning light should come on when you first start the ignition and then go out. If the oil warning light comes on when you're driving, it's telling you that the oil pressure is low (due to a serious leak, very low oil level, or engine wear) - stop at once.
What sort of oil do I need? Always use an oil that meets the car maker's specifications. A cheap oil is a false economy. Look on the packaging to see what the thickness of the oil – the SAE rating – and the quality of the oil shown by the API or ACEA rating. If there's no rating, don't buy it. The highest quality oils are fully synthetic but a semi-synthetic oil should do the trick and always use the oil quality recommended by the car manufacturer.
To do an oil level check the engine should have stopped for at least 5 minutes and the car should be parked somewhere level. Take a clean cloth, your engine oil and a funnel.
- Take the dipstick (it's probably a bright colour) and pull it out of its tube.
- Take your clean cloth and wipe the dipstick down.
- Push the dipstick slowly all the way back into its tube, then pull it out again. The level should be between the upper and lower oil level marks.
- If the level is near the lower mark, then top up. First find the oil cap on top of the engine (check in your car handbook if you're not sure).
- Unscrew the cap and pour a small amount of oil in. Pouring in too much can cause leaks.
- Check the oil level again after a minute or so. Top up if you need to so the oil reaches the dipstick, then screw the filler cap on tightly and replace the dipstick in the tube.