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Oil Filter Size: Why Are Oil Filters Different Sizes?

A white oil filter installed in the engine bay of a car

Life tends to offer choices, and this is certainly true when it comes to oil filters. A visit to an automotive store will make it clear that the oil filters on the market range from small to large. Why do oil filters come in different sizes, and is oil filter size important? Here we’ll answer these questions.

What Does an Oil Filter Do?

An oil filter plays a key role in the health of your car’s engine. Motor oil keeps your engine lubricated, and it also absorbs contaminants that the engine is exposed to while it’s in operation. These contaminants can be classed into two main groups:

  • Organic contaminants, such as bacteria and bugs.
  • Inorganic contaminants, such as dust, metallic particles and debris caused by engine wear.

Oil filters support the engine by keeping your car’s motor oil free of organic and inorganic contaminants that may find their way into the engine as your car operates or as you work on it. This helps to improve your car’s performance and extends the life of its engine.

Why Do Oil Filters Come in Different Sizes?An oil filter can help optimize the life of your car's engine.

Oil filters all perform the same general role: They help keep motor oil clean and hold contaminants. Some engines, such as those in simple passenger cars, require only a small filter to handle the relatively small amount of oil in the vehicle. Larger or higher-powered engines, such as those in heavy-duty hauling vehicles or performance cars, will require more oil flowing at a higher rate to keep things cool and lubricated, which means they’ll need a bigger filter.

Different filters can also perform different duties on different vehicle . Here are some examples of oil filter types and the roles they serve:

  • Primary oil filter: This type of oil filter is also known as a full-flow filter. It’s responsible for filtering all of the oil that passes through your car’s engine. You’ll find this type of oil filter in most car engines.
  • Secondary oil filter: This filter cleans up to 10% of a vehicle’s motor oil. It’s typically used in addition to a primary oil filter. If your vehicle wasn’t originally equipped with a secondary oil filter, you can choose to install one after purchasing the vehicle.
  • Thermal chamber oil filter: A thermal chamber oil filter raises the temperature of the oil. This is done to burn off harmful contaminants. To do their work, these filters consume electricity, which can reduce fuel efficiency.
  • Spinner filter: Spinner filters are also referred to as centrifugal filters. They clean engine oil by using a spinning motion to capture contaminants.
  • Magnetic oil filter: A magnetic oil filter is designed to clean certain metal contaminants out of your oil. Keep in mind, though, that this filter doesn’t work on impurities such as dust and bugs.

Which Oil Filter Should I Choose?

The best oil filter for your vehicle is the one that’s recommended by your car’s automaker. This information will be listed in your car’s owner’s manual. The manual will also provide guidance that lets you know how frequently the oil filter needs to be maintained or replaced. If you know your car already has the correct filter installed, you could also simply make a point of replacing it with the exact same make and model.

Engine repair can be costly, so be sure to check your oil frequently and change it when necessary, always replacing the filter with a fresh one. By doing so, you can help keep your vehicle on the road for years to come.

Check out all the engine oil filters available on NAPAonline, or trust one of our 17,000 NAPA Auto Care locations for routine maintenance and repairs. For more information on oil filter size, chat with a knowledgeable expert at your local NAPA Auto Parts store.


Warren Clarke View All

I'm a writer and editor who's a regular contributor with the New York Daily News and Carfax, and my content has appeared in over 20 publications. I've written content that covers industries such as automotive, medical, insurance, healthcare, real estate, plumbing, pest control, dental and hospitality.

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