Car oil filter guide article highlights:

• Virtually all cars use either a spin-on or a cartridge full-flow oil filter
• A cartridge filter separates the spin-on filter’s components; some stay with the car while the filter media itself is replaced
• While certain types of filter media last longer and filter finer particulates, they’re compatible with all oil types, synthetic or conventional

Owning a car involves a lot of important maintenance tasks, but changing your oil is perhaps the most vital. It’s not called the engine’s lifeblood for no reason: oil cleans, lubricates, and helps regulate temperatures. And besides checking and changing the oil, you also have to replace your car’s oil filter. But nowadays, there are practically as many filter options as there are oils, which can turn a seemingly simple task into analysis paralysis. With the handy guide below, though, it doesn’t have to be difficult.

There’s more than one type of car oil filter

Your car has several vital filters scattered throughout, and the oil filter is one of them. As noted earlier, the oil keeps your engine running smoothly by reducing friction and picking up contaminants that can damage components. Whether it’s soot, metal shavings, random fibers, etc., your oil usually catches it. However, because your oil system is fully-contained, there’s nowhere for this crud to go—that is, unless there’s a dedicated filter.

This type of singular oil filter, an arrangement basically all passenger car engines use, is called a ‘full-flow filter,’ Your Mechanic explains. That’s because it filters the engine’s full oil flow. Some engines also have secondary filters to back up the full-flow ones, but they’re not the focus of this guide.

Full-flow oil filters fall into two broad categories: spin-on and cartridge. Spin-on filters have been the dominant type for decades, but cartridge filters are making a comeback for reasons we’ll explain shortly. And while the two are similar in several ways, they’re not identical.

The anatomy of a spin-on car oil filter

Let’s start with the more-common spin-on oil filter, which is usually housed in a steel canister.

At the bottom of the canister is the baseplate/tapping plate, which is where the oil enters/exits the filter, The Drive explains. This is also where the leak-preventing sealing gasket, which is usually a rubber O-ring, sits. Immediately behind the baseplate is the anti-drain back valve. This keeps dirty oil from flowing back into the engine and clean oil from getting sucked back into the filter.

Speaking of dirty oil, it flows into the filter’s sides through the holes in the baseplate. That’s when it encounters the filter’s critical component, the filter media. This is what actually filters the oil, and it’s usually pleated to increase its surface area and therefore its efficiency. Once the oil is filtered, it flows into the center tube, typically made of steel, and back into the engine.

To keep dirty oil from accidentally getting into the tube, some companies install end discs or close the ends with sealant. And to make sure everything fits together tightly, and thus works properly, there’s a coil or leaf retainer spring at the end of the canister.

In addition, cold oil doesn’t flow well, especially at startup, which also means it doesn’t filter easily. So, to prevent pressure-related filter damage and potential oil starvation, these filters have spring-loaded relief/bypass valves that temporarily let unfiltered oil pass through the center tube. These valves also open if the filter media is completely clogged, The Drive notes, or if the filter is the wrong size. Hence why you should change the filter with every oil change and make sure you have the right one.

Cartridge vs. spin-on filters

At first glance, cartridge oil filters look like bare pleated media. That’s because all the metal components and valves are found either in the base of the housing or in the filter’s cap. It’s almost like a deconstructed spin-on filter in that regard.

Admittedly, cartridge filters make oil changes more complicated. Rather than spinning a one-piece canister on and off, you have to remove the cap, fish the cartridge out, and put the cap back on. However, the filter cartridge doesn’t have any metal parts. That makes it significantly easier to recycle, The Drive explains. And because the various metal springs and valves stay with the car, cartridge filters are significantly easier and cheaper to manufacture.

Also, remember how the notion of filter size came up earlier? Oil filter sizes vary based on several factors, but in general, bigger engines require proportionally larger filters. With many OEMs downsizing and turbocharging their engines, large spin-ons are giving way to compact cartridges. Case in point, my parents’ 2.5-liter naturally-aspirated Mazda CX-5 has a spin-on filter, while my 1.6-liter turbocharged 500 Abarth has a cartridge one.

Oil filter media literacy: how filter material affects oil change intervals and filtration quality

Interestingly, my 1.8-liter NB Miata used a spin-on oil filter, rather than a cartridge one. However, that’s also because of the filter media limitations of the time. And it’s another reason why cartridge filters are rising in popularity and spin-on filters are shrinking.

All filters—oil, air, etc.—work by physically stopping debris from passing through their media. But the media can only stop debris above a minimum size. And it can only trap so much gunk before it clogs completely.

One way to improve filtration is to have more media, which means a physically larger filter. Another option is to increase the filter media’s surface area, such as by pleating. Alternatively, you could switch out the kind of media the filter uses.

Cellulose media is cheap, but it only lasts about 3000 miles, can’t filter out some of the finest particles, and doesn’t provide as many passages for oil, YM claims. Synthetic media is more expensive, but it lasts about twice as long, filters out more particles, and restricts oil flow less. And micro-glass media is pricier still, but it’s even more effective and longer-lasting. Keep in mind, though, these are general statements: always follow your car’s recommended oil-change interval.

With many modern ‘long-life’ oil filters using synthetic or partially-synthetic media, spin-on filters don’t have to be large to be effective. And because cartridge filters are just as effective but more eco-friendly and even simpler and lighter, some OEMs are biting the bullet and ditching the spin-on.

Do different oil grades or synthetic oils require specific filters?

It’s not an age-old question, but it is a common one: should you go conventional or synthetic with your engine oil? And that raises another question: does that decision impact your filter choice?

Some sources, including The Drive, say it does, with some caveats. Although synthetic oil will filter through cellulose media just fine, the oil likely has more longevity than the media. Hence why, if you’re using synthetic oil, you really should use a filter with synthetic media. However, as long as your car’s manufacturer doesn’t require it, it’s not necessary.

It’s a similar story with different oil grades. Barring exotic racing stuff, your filter doesn’t really care about the grade. Your average spin-on or cartridge works with 5W-40, 10W-30, 0W-20, and everything in between. Just make sure whatever filter you have fits your car.

Where can you look up which filter you need?

If you’re getting ready to change your own oil but don’t know which filter to get, there are several ways to find out.

Firstly, any major auto parts store’s website lets you search for compatible filters using year, make, and model. You search the same way if you want to buy directly from a supplier like K&N or your OEM.

If for some reason you can’t access the information virtually, you could always bring an old filter into a store or dealership service department. While that means parking your car, it’s still an option worth considering in a pinch. And it’s worth noting that you should bring old filters to auto parts stores or public services for recycling.

Can you change the type of filter your car uses?

As noted earlier, cartridge oil filters aren’t quite as easy to replace as spin-on ones. But could you modify your engine to accept a spin-on instead of a cartridge?

Technically, yes. Some aftermarket shops and suppliers make adapter kits so cars use spin-on oil filters instead of cartridge ones. This is especially useful for classic car owners, as vintage cartridges are often messier than modern ones. Plus, not only can these adapters make oil changes easier, but they also remove the risk of damaging the cartridge’s cap.

However, a few words of warning. One, not every car engine has an adapter kit. Two, kit availability is no guarantee of quality. Three, while oil filter housings sometimes require replacement, modifying them introduces a host of additional variables and potential failure points. Also, it means using a completely different filter than your car’s manufacturer designed it for.

Admittedly, this is a lot of information to keep track of. But hopefully, it makes oil filter shopping a little bit easier.

Follow more updates from MotorBiscuit on our Facebook page.