What Are the Causes of Car Oil Leaks?

Updated April 17, 2017

All cars will eventually develop some type of oil leak. Leaks can range from minor seeping problems to more serious flaws. A vehicle that slowly drips oil is not a major threat to the functioning of the car, but the oil does stain garage floors and driveways. More serious leaks, if left unattended, can result in internal damage to the engine. Oil leaks can be very difficult to find. However, you can save a lot of time and hassle by considering the most common causes of oil leaks. First, do a quick overview of the basics--oil filter, oil drain plug and the oil cap. One of these could easily be the source of the problem. Second, the most common cause of oil leaks is the valve cover gasket. This is a more difficult problem to diagnose.

Oil Filter

A common cause of oil leaks is a loose, improperly aligned or worn-out oil filter. You can avoid problems by changing the oil filters every time the oil is changed. The oil filter will leak if it is not tight enough. If it has not been installed properly this can also cause a leak. If you have a mechanic change the oil, make sure that the oil filter has been replaced.

Oil Pan Drain Plug

The drain plug is at the bottom of the oil pan, which is on the underside of the car. The drain plug could be loose, or it may not be threaded correctly. If this is the case, adjust the plug so it fits tightly. It may be worn out and in need of replacement.

Oil Filler Cap

The oil filler cap covers the hole where you put oil in the engine. If the cap is missing, loose or broken, pressure from the engine will cause the oil to spill out.

Valve Cover Gasket

The valve cover gasket is the most common cause of oil leaks. A gasket is a seal, usually made from rubber or silicone, that is used to join two metal parts and prevent leakage.The valve cover sits at the top of the motor and is bolted to the engine. Oil is pumped from the bottom of the engine to the top and pools under the valve cover. The oil slowly drips back into the engine through drainage holes. Infrequent oil changes result in build-up of sludge, which restricts the flow of oil back into the drainage holes. Sludge is the name for engine oil that breaks down over time because of prolonged exposure to high temperatures, leaving baked-on oil deposits. Sludge exerts greater pressure on the valve cover gasket, degrading its ability to function as a proper seal.

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About the Author

Robert Russell began writing online professionally in 2010. He holds a Ph.D. in philosophy and is currently working on a book project exploring the relationship between art, entertainment and culture. He is the guitar player for the nationally touring cajun/zydeco band Creole Stomp. Russell travels with his laptop and writes many of his articles on the road between gigs.