Oil is one of the most vital fluids in your car, it provides essential lubrication for the moving components inside the engine. Unfortunately, as the oil is pumped all around the engine at high pressure, oil leaks can develop in various ways.  

We go through the potential costs of fixing an oil leak, and discuss the common causes and fixes.  

Is An Oil Leak Serious? 

Yes, if your engine is leaking oil you are constantly running the risk of premature engine wear or failure. Oil is vital to the running of your engine, and you won’t get any warning signs the engine is about to break. 

Not only is an oil leak harmful to your engine, it can cause a number of issues for other road users and animals. Oil leaking onto the road becomes extremely slick when wet, causing an extremely dangerous surface for driving on.  

Is it normal for an old car to leak oil? 

In years gone by, it was normal for a car to leave a drop or two of oil on the floor whilst parked. Any leak from a modern car however, especially if regularly seen, should be cause for investigation.  

However, a few spots of oil may not always mean disaster and large repair bills. It could be something as simple as some overspill from your last oil change or top-up. If it happens regularly, definitely book an inspection from a mechanic. 

Can You Drive With An Oil Leak 

Whether or not you can drive with an oil leak depends on the severity and distance. If you notice one or two very small spots on the ground, it’s probably okay to drive a few miles to the garage.  

A leak much larger, or distance much longer, and we’d definitely suggest leaving the car where it is until you can get it inspected properly. This is both to protect your wallet and other road users. 

How Much Does It Cost To Repair An Oil Leak?  

If you have an oil leak coming from your engine, it’s vital to get it sorted as soon as possible. Below we’ve compiled a list of UK cost estimates for various causes of an engine oil leak. These causes are further explained below.  

• Cost to repair a leaking valve cover gasket: £160 - £500 
• Cost to repair a leaking rear main seal: £450 - £2,000 
• Cost to repair a leaking oil sump gasket: £125 - £375 

Split the cost of repairs and services into interest-free monthly payments at trusted dealerships and garages.

How do you tell if you have an oil leak in your car? 

If you’re concerned your engine is leaking oil, there are a few checks you can carry out: 

1. Check the level regularly - If your oil level is dropping when not using the car, or much faster than normal, it's quite possible a leak has developed. 
2. Have a look under the bonnet - check around the front, back and sides of the engine as best you can. Using a torch to see any spots of wetness on the engine itself. Check underneath - Oil is reasonably sticky, so will generally run down the side of the engine and drip off the lowest point. Look around the edges of the engine or undertray for drips or shiny, wet spots. 
3. Use some cardboard - If you can't see any oil coming from the engine, but do notice black marks on the floor that make a rainbow pattern when it rains, place a large piece of cardboard under the engine overnight. This will catch any drips and make them much more visible. 

Common Causes for Oil Leaks and How to Check For Them 

Whilst engine oil is pumped to pretty much every part of an engine, there are a few common spots that can develop leaks. Most of these are where rubber seals are used to contain the oil inside the engine.  

Oil filter housing or sump plug 

During its cycle around the engine, the oil is filtered to remove contaminants. This filter is changed as part of your regular service. During this job, the oil filter and sump plug will be removed, if these are not properly re-installed, they could leak. 

How To Check 

To check, and locate your oil filter, check some online guides for changing the oil on your specific model if you’re unsure. Check for a film or runs of oil on or around the filter. If it's dirty, wipe it clean and check again after a drive. 

Overfilled oil 

Because the air pressure inside the crankcase changes during normal use, a vent is fitted, called the crankcase breather. If the engine has been overfilled with oil the pressure can cause it to escape through this pipe. 

How To Check 

Most modern cars will have the crankcase breather buried under other components, this one is best to ask a garage to look out for, if you can't see any other sources for the leak. 

Bad gaskets 

To contain the oil inside the engine, many different gaskets are used, these can perish as they get old, and allow oil to leak from the engine, making them one of the top oil leaks causes. 

How To Check if a Perished Gasket is Causing a Leak 

Common gasket leaks include: 

• Camcover gasket - Look around the top of the engine, for wet or shiny patches of fresh oil
• Timing chain gasket - First check if your car has a chain or belt, if it has a chain, these operate in engine oil. On the side of the engine (or front if it's rear-wheel drive) will be a metal or plastic cover from top to bottom, check around the split lines where this attaches to the engine.
• Sump gasket - The very lowest point on the engine is the sump, check for wet or shiny patches at or below the line at which this is attached to the engine - this may be difficult without removing the undertray. 
• Oil pump gasket - usually on the front or side of the engine, this may also be difficult to check without removing parts.  

Broken or perished seals 

Seals do the same job as gaskets, but differ in that they generally seal moving components.  

How To Check 

Seals you may see leaks from include: 

• Rear main seal - seals between the engine output shaft and the engine. The only way to check this without removing the gearbox is to check for leaks emanating from where the engine attaches to the gearbox, under the car. 
• Camshaft seal - found on the top of the engine, sealing the point where the camshafts exit the head. This is hard to check for, without removing the cam cover, but oil is likely to run to the bottom of the engine, down the left-hand side 

What Does It Mean If Oil Is Dropping But There’s No Leaks?

If you’re noticing your oil level is dropping, but no oil is on the floor after driving or parking, the oil may be entering the combustion chamber or water system. Telltale symptoms would be blue smoke from the exhaust or a yellowy substance in the coolant. 

For more information, check our guide on engine smoke and what it means. 

Split the cost of repairs 

With Bumper, you can split the cost of repairs into monthly payments at no extra cost. Apply online for up to £5,000 and choose from 1,000s of trusted repairers. 

Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.