Oil Filter Leak: Causes and Fixes

Your engine needs oil to run, and even with frequent changes, it’s possible for debris and impurities to find their way into the lubrication system over time and wreak havoc. That’s where the oil filter comes in.

Filters protect your engine from major damage and provide an easy point of maintenance that can extend the life of your vehicle by years if they receive proper attention. An oil filter leak can compromise these gains, but if you understand what causes a leak and how to avoid it, you can take steps to keep your engine in prime condition longer.

How an Oil Filter Functions

The moving parts of an engine have very tight tolerances that need to be well-lubricated with clean oil to prevent excessive friction and heat as the engine runs. The car’s oil pump pressurizes the engine oil, sending it through the oil filter, which traps any potentially damaging impurities before they can flow into the engine. The filter must be changed regularly — usually during an oil change — to avoid becoming clogged.

The filter threads onto an oil filter housing on the engine. It has a hard but thin metallic exterior and a rubber gasket around the head that contacts the mating surface of the housing, ensuring a leak-tight seal that can handle the vibrations of normal operation.

Sneaky Leaks

There are a few reasons why a filter might leak.

When the oil in your vehicle is moving from one component to another, it’s under a lot of pressure. If the oil filter is installed too loosely, it can vibrate loose and allow oil to leak out. If it’s installed too tightly, the gasket could be damaged, leading to a leak.

Leaks can also occur during an oil change if the gasket from the old filter sticks to the housing. When the new filter twists on, you’ve suddenly got two gaskets, which can leave you with a leak and, soon after, a burst. A new gasket could also bind, crimp or otherwise become unseated during installation.

Beyond the gasket, you must make sure that the soft metal threads on the filter’s mouth aren’t damaged or screwed in incorrectly. It’s also possible to have the wrong filter altogether, as many filters look similar but are specific to certain engines. Be sure to verify for compatibility.

The filter housing on the engine can also be damaged, or the mating surface between filter and housing could be dirty enough to allow oil through. Finally, there’s always the possibility of physical damage to the filter from impact.

The Fix

The best way to avoid leaks is to be proactive at the time of installation. When you remove old filters, ensure that the housing is free of debris and old gasket material so there’s a clean mating surface. While you’re there, inspect the new filter for dents, damaged threads, and cut or warped gaskets — and double-check that you’re using the right filter number. Smear a light layer of oil around the gasket so it doesn’t bind on installation, and carefully thread it onto the engine by hand, taking care not to overtighten. As always, refer to your manufacturer’s recommended torque for this piece. Finally, check the oil level and top off as needed.

It’s important to note that if you have a serious oil leak, you should stop the engine immediately and tow the car to a shop for repairs. If there are just a couple of drops and you’d like to diagnose the issue yourself, start by cleaning the area so you can see where the leak first appears. This should help you identify the source quickly. As always, be sure to take proper safety precautions when you’re working on a running or hot vehicle.

Check out all the oil filters available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on an oil filter leak, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Blair Lampe.