Engine oil keeps the moving parts inside your engine from grinding against each other, carries heat away and holds dirt in suspension until the filter catches it. Old or low oil is one of the quickest ways to shorten an engine's life, so it's worth knowing how often to change it and how to check the level yourself.
How often should you change your oil?
The honest answer is: as often as your car's manufacturer says. Oil change intervals vary a lot between engines, oil types and driving conditions.
Where to find your interval
- The owner's manual or service book: lists the interval in miles or kilometres and in time (for example "or every 12 months"), whichever comes first.
- The oil-life monitor: many modern cars calculate oil life from how the car is actually driven and show a message when a change is due.
- Your dealer or garage: can confirm the schedule for your exact engine.
Is the 3,000-mile rule still true?
For most modern cars, no. The 3,000-mile (about 5,000 km) rule dates from older engines and oils. Many modern cars using synthetic oil have recommended intervals of several thousand miles or more, and some longer still, according to their manufacturers. Changing oil far more often than recommended mostly costs money. Changing it less often than recommended risks engine wear.
Change it sooner in "severe" conditions
Most manuals list a shorter interval for severe service. This often includes:
- lots of short trips where the engine doesn't fully warm up,
- stop-and-go city traffic,
- towing or carrying heavy loads,
- very hot, cold or dusty conditions,
- extended idling.
Many everyday drivers actually fit the severe category, so check which schedule applies to you.
Don't forget the time limit
Even if you drive very little, oil ages. Most manufacturers recommend changing it at least once every year (or the period stated in your manual), regardless of mileage.
Choosing the right oil
Use the oil viscosity (for example 0W-20 or 5W-30) and specification listed in your owner's manual. Many manufacturers require oil that meets a specific approval or standard, especially for diesels with particulate filters and for engines with long service intervals. The wrong oil can affect warranty, fuel economy and engine protection.
How to check your oil level
Checking the oil takes two minutes and is worth doing regularly, such as every few fill-ups and before long trips. Some engines naturally use a little oil between changes.
Step 1: Park on level ground
A slope gives a false reading.
Step 2: Turn off the engine and wait
Most manuals say to wait a few minutes after switching off so the oil drains back into the sump. Some manufacturers specify checking with the engine warm. Follow your manual.
Step 3: Find the dipstick
It usually has a brightly coloured handle (often yellow or orange) and is marked with an oil-can symbol. Some newer cars have no dipstick and show the oil level on the dashboard instead. Check your manual if you can't find one.
Step 4: Pull, wipe, reinsert, pull again
- Pull the dipstick out and wipe it clean with a cloth.
- Push it fully back in.
- Pull it out again and look at where the oil film ends.
Step 5: Read the level
The dipstick has two marks, dots, holes or a hatched area showing minimum and maximum.
- Between the marks: fine.
- At or below minimum: top up.
- Above maximum: too much oil can also cause problems. Have the excess drained.
On many cars, the difference between the minimum and maximum marks is roughly one litre (about one quart), but this varies. Your manual will say.
Step 6: Look at the oil
- Amber to dark brown and smooth: normal. Oil darkens quickly in many engines, so colour alone doesn't mean it needs changing.
- Milky or frothy: can indicate coolant mixing with oil. Get it checked.
- Gritty or smelling strongly of fuel: have it checked.
How to top up
- Use the correct oil for your engine.
- Remove the oil filler cap on top of the engine, which is marked with an oil-can symbol. This is not the dipstick tube on most cars.
- Add a small amount at a time, using a funnel.
- Wait a minute, then recheck with the dipstick. Don't overfill.
- Refit the cap securely.
Warning signs of an oil problem
- Red oil pressure warning light: stop as soon as it's safe and switch off the engine. Low oil pressure can destroy an engine quickly. See our dashboard warning lights guide.
- Ticking or knocking noises from the engine.
- Burning oil smell or blue smoke from the exhaust.
- Oil spots under the car. A clean engine bay makes leaks easier to find. See how to clean a car engine bay safely.
Engines that burn oil can also damage the catalytic converter over time. Our P0420 guide explains why.
Should you change your own oil?
You can, with the right tools, a safe way to lift the car (proper axle stands, never just a jack), the correct oil and filter, and a way to dispose of old oil responsibly. Many recycling centres and parts stores accept used oil. If any of that is a problem, a garage oil change is usually one of the more affordable services, with prices varying by car, oil type and location.
If you see a warning light or notice a leak and want to know how urgent it is, describe it on GrepKit's free car checker.
Frequently asked questions
How often should I check my oil level?
A good habit is every few fill-ups, and always before a long trip. Check more often if your car is older, has a known leak, or your manual says the engine may use some oil between changes.
Can I go over my oil change interval?
Going slightly over occasionally isn't usually a disaster, but regularly exceeding the interval increases engine wear and can affect warranty claims. Stick to the mileage or time limit, whichever comes first.
Does synthetic oil last longer?
Synthetic oils generally resist breakdown better and are required for many modern engines with longer intervals. The right interval is still whatever your manufacturer specifies for your engine and oil.
What happens if I put too much oil in?
Overfilling can cause the oil to froth, reduce lubrication, increase pressure on seals and, on some cars, damage the catalytic converter. If you're well above the maximum mark, have the excess drained.