A dark patch under the car on the drive, a burning smell after a long run or an oil level that keeps dropping between services are all signs that your engine is leaking oil. Most leaks start small and are cheap to fix. A few sit deep inside the engine and cost far more, and some can damage other parts if they are ignored. Here is how to find where the oil is coming from, what each repair typically costs in the UK, whether the car is safe to drive and where a warranty fits in.
Is your car really leaking oil?
Before you book anything, make sure the fluid is engine oil. Slide a sheet of white card or kitchen paper under the engine overnight and look at the colour in the morning.
| Colour and feel | What it usually is |
|---|---|
| Light brown to black, slippery | Engine oil |
| Red or pink, thin | Automatic gearbox fluid or older power steering fluid |
| Green, pink, orange or blue, sweet smell | Coolant (antifreeze) |
| Clear and odourless | Water from the air conditioning, which is normal |
| Yellowish to light brown, very slippery, near a wheel | Brake fluid: do not drive, get the car checked |
Not every oil leak leaves a puddle. Oil that drips onto a hot exhaust burns off before it reaches the ground, so the only signs may be a burning oil smell, blue-grey smoke from under the bonnet or an oil level that drops between checks. If the level falls but the engine is dry and there is blue smoke from the exhaust, the engine is more likely burning oil internally than leaking it, which is a different problem covered further down.
The most common causes of an oil leak
Oil is kept inside the engine by gaskets between metal parts and by rubber seals where shafts come out of the engine. Over years of heating up and cooling down, these harden, shrink and start to weep. The usual culprits, roughly from most to least common, are:
- Rocker cover (valve cover) gasket. The gasket under the cover on top of the engine. Very common on older cars, and oil running down the side of the engine or onto the exhaust manifold is the giveaway. It is also the source of most burning smells.
- Oil filter or sump plug. A filter not tightened properly, a double gasket left on after a service or a sump plug with a worn washer. Cheap to fix, and worth checking first if the leak started right after a service.
- Sump gasket. The seal between the oil pan and the bottom of the engine. On many modern cars this is a bead of sealant rather than a gasket. Sumps can also crack or dent if the car grounds on a speed bump.
- Oil cooler or oil filter housing seals. Common on many BMW, MINI, Vauxhall and Ford engines. The leak can mix oil and coolant, so it needs dealing with quickly.
- Camshaft and crankshaft front oil seals. Round seals behind the timing belt or chain. A leaking seal here can contaminate a timing belt, which is why garages often renew them during a cambelt change.
- Turbo oil feed and return pipes. On turbocharged engines, the small pipes that carry oil to and from the turbo can weep at their joints.
- Rear main seal. The seal at the back of the crankshaft, between the engine and the gearbox. Oil dripping from where the engine meets the gearbox is the clue. The seal itself is cheap but the gearbox has to come out to reach it.
- Head gasket. An external oil leak from the head gasket is less common than coolant loss, but it happens. See our head gasket guide.
How a garage finds the leak
Oil spreads. It runs downhill, gets blown backwards by the air flow under the car and collects on the lowest point, which is often nowhere near the source. A good garage will usually clean the engine with a degreaser, run it, and look for fresh oil. For stubborn leaks they add an ultraviolet dye to the oil and trace it with a UV lamp after a short drive. Expect to pay around £40–£90 for a diagnosis on its own, though many garages waive it if they do the repair.
It is worth paying for the diagnosis. Replacing the rocker cover gasket because there is oil on the side of the engine, only to find the real leak is a cam seal below it, is a common and avoidable waste of money.
How much does an oil leak repair cost in the UK?
The price depends almost entirely on where the leak is and how much of the engine has to come apart to reach it. These are typical independent-garage prices including parts, labour and VAT for an average petrol or diesel car. Main dealers and premium or V6/V8 engines will be higher.
| Repair | Typical UK cost |
|---|---|
| Sump plug washer or oil filter refit | £20–£60 |
| Rocker cover gasket (4-cylinder) | £100–£250 |
| Rocker cover gasket (V6 or BMW straight-six) | £250–£500 |
| Sump gasket or reseal | £150–£400 |
| Replacement sump (cracked or damaged) | £200–£500 |
| Oil filter housing or oil cooler gasket | £150–£450 |
| Camshaft or crankshaft front seal | £150–£400 (less if done with a cambelt change) |
| Turbo oil feed or return pipe | £120–£350 |
| Rear main seal (manual gearbox) | £350–£800 |
| Rear main seal (automatic or 4x4) | £600–£1,200 |
If the rear main seal is leaking on a manual car, the garage has to remove the gearbox and clutch to get to it. If the clutch is already worn, it often makes sense to fit a new one at the same time, because you have already paid for most of the labour. Ask for a quote with and without the clutch. Our clutch cost guide explains the prices.
What about oil leak stop additives?
Bottles of "stop leak" contain chemicals that make rubber seals swell slightly. On an old car with a small weep from a hardened seal they can sometimes slow a leak for a while. They do nothing for a cracked sump, a loose filter or a gasket that has split, and they are not a repair. If you use one, keep checking the oil level, and tell the garage you have used it.
Is it safe to drive with an oil leak?
A slow weep that leaves a few spots on the drive is not an emergency, as long as you keep the oil topped up and get it looked at. Check the level on the dipstick (or in the car's menu, if it has no dipstick) once a week until it is fixed. There are three situations where you should not drive on:
- The red oil pressure warning light comes on. Stop as soon as it is safe and switch off. Driving with no oil pressure can destroy the bearings, the turbo and the timing chain in minutes. Our warning lights guide explains what to do next.
- Oil is dripping onto the exhaust and you can see smoke. Oil on a hot exhaust manifold is a fire risk.
- You are losing more than about half a litre a week, or the level is below the minimum mark. A large leak can empty the sump quickly, and low oil is one of the commonest reasons an engine fails.
A leak can also damage other parts. Oil softens rubber engine mounts, coolant hoses and suspension bushes, it can ruin a timing belt, and oil dripping onto the clutch can cause it to slip. The longer a leak is left, the bigger the eventual bill tends to be.
Oil leaks and the MOT
An oil leak is not an automatic MOT failure. The tester will record an advisory for a minor leak. It becomes a major defect (fail) when oil is leaking so much that it poses a risk to the environment or other road users, which in practice means a continuous drip rather than a damp engine. A fluid leak that is likely to cause a fire, or brake fluid leaking, is a dangerous fail. If your last MOT listed "oil leak" as an advisory, it is worth getting it fixed before the next test, when it may have got worse. See our list of the most common MOT failures.
Leaking oil or burning oil?
If the oil level keeps falling but there are no spots under the car and the engine is dry, the oil is probably being burned inside the engine. Signs include blue smoke from the exhaust, especially when you start up or accelerate after idling, and oily spark plugs on a petrol engine. Common causes are worn piston rings, worn valve stem seals, a failing turbo seal or a blocked crankcase breather (PCV) system.
Some modern engines are known for using oil even when healthy, and manufacturers often allow up to around a litre per 1,000 miles. Burning oil from worn rings or a failing turbo is a much bigger job than a leaking gasket, so it is worth a proper diagnosis. Our guides to turbo replacement and engine replacement costs show the prices at the top end.
Does a car warranty cover an oil leak?
It depends on what is leaking and why. Mechanical breakdown warranties are built to pay for the sudden failure of a covered part. Gaskets and seals that have simply aged and started to weep are often treated as wear, and many policies only cover oil seals and gaskets when they are replaced as part of an authorised repair to a covered component. A cracked oil cooler, a failed turbo oil seal or an internal engine fault that causes oil loss is a different matter, because the leak is a symptom of a covered part failing.
Always check the What Is Covered schedule for your own policy rather than assuming. With ClearPath, eligible claims are covered up to £3,000 per claim, including parts, labour and VAT, with labour up to £100 an hour, a £100 excess and no limit on the number of eligible claims. The garage must contact us and get authorisation before any work starts. Keep your oil topped up and your service history up to date, because a claim for engine damage can be refused if the engine was run low on oil.
On its own, a rocker cover gasket is not the repair that makes a warranty worthwhile. The case for cover is the larger bills that an oil problem can lead to on an older car, such as a timing chain, a turbo or the engine itself.
How to stop oil leaks happening
- Service on time with the right oil. Oil of the wrong grade, or oil left in too long, breaks down and is harder on seals.
- Do not overfill. Too much oil raises pressure in the crankcase and pushes oil past seals.
- Keep the breather system clear. A blocked PCV valve builds pressure inside the engine, one of the commonest hidden causes of multiple leaks at once.
- Check under the car now and then, especially after a service, and look at the level every couple of weeks on an older car.
- Go easy over speed bumps on lowered or low-slung cars, where the sump is the lowest point.
For more ways to keep an older car healthy, read how to make your car last.
The bottom line
Most oil leaks come from a tired rocker cover gasket, sump gasket or oil filter and cost roughly £100–£400 to fix at an independent garage. The expensive one is the rear main seal, at around £350–£1,200, because the gearbox has to come out. Pay for a proper diagnosis before replacing parts, keep the oil topped up until it is fixed, and stop at once if the red oil light comes on. To see what cover costs for your car, get an instant quote.
