What an oil filter does and why it matters
An oil filter removes dirt, metal particles, and sludge from your engine oil as it circulates. Over time, the filter traps enough debris that it becomes clogged and stops working well. A clogged filter forces oil to bypass it entirely, which means dirty oil reaches your engine parts — this causes faster wear and can shorten engine life. Replacing the filter every time you change your oil keeps the system working as designed.
The filter itself is a metal canister or cartridge filled with pleated paper or synthetic material. As oil flows through, the material catches particles while letting clean oil pass. When you change your oil, you drain the old filter and screw on a new one (or slide out a cartridge and insert a fresh one, depending on your car's design).
Key Takeaways
- Your owner's manual lists the exact filter part number and type your car needs — this is the most reliable way to find the right one.
- Oil filters come in spin-on (screw-on) or cartridge styles; your car uses one or the other, not both.
- Aftermarket filters from auto parts stores cost less than dealer filters but must meet the same pressure and flow standards your engine requires.
- A new filter should be hand-tightened only — over-tightening damages the seal and causes leaks.
- Replacing the filter at every oil change is the standard practice; some filters last longer, but changing both together is simpler and safer.
Finding your car's filter type and part number
The owner's manual is your starting point. It lists the exact filter part number, the thread size, and whether your car uses a spin-on or cartridge filter. If you do not have the manual, you can find it free online by searching "[your car year, make, model] owner's manual PDF" or by visiting your car manufacturer's website.
Once you have the part number, you can search it at any auto parts store — online or in person — and they will show you the filter and confirm it fits your car. Some stores also let you search by vehicle year, make, and model instead of part number, which works if you enter your information correctly.
If you are unsure whether your car has a spin-on or cartridge filter, the manual will say. Spin-on filters look like a metal can with a threaded base; you screw them onto a bolt on the engine. Cartridge filters are usually cylindrical and sit inside a plastic or metal housing on top of the engine; you unscrew the housing cap, pull out the old cartridge, and drop in a new one.
Spin-on filters: the most common type
Spin-on filters are threaded at the base and screw directly onto a bolt protruding from the engine. They are the easiest to replace because you do not need to open any housing or deal with internal seals. When you unscrew the old one, a small amount of oil drains out, so have a drain pan or old towel ready.
Spin-on filters come in different sizes and thread pitches (the spacing of the threads). The wrong size will not screw on, or will screw on but leak. This is why using your part number or owner's manual is essential — guessing by appearance leads to mistakes. Common sizes include 3/4-16 and 3/4-20 threads, but others exist.
When you install a new spin-on filter, you hand-tighten it until the rubber seal on the base touches the engine, then turn it an additional three-quarter turn. Do not use a wrench or filter wrench to tighten it further — over-tightening crushes the seal and causes leaks. The filter will tighten slightly more as the engine warms up and the seal expands.
Cartridge filters: sealed inside a housing
Cartridge filters sit inside a plastic or metal housing bolted to the engine. To replace one, you unscrew the housing cap (usually a large plastic nut or bolt), lift out the old cartridge, and insert a new one. The housing itself stays in place; only the cartridge is replaced.
Cartridge filters have an internal seal or gasket that sits between the cartridge and the housing cap. When you install a new cartridge, you slide it into the housing and screw the cap back on hand-tight, then turn it an additional three-quarter turn — the same rule as spin-on filters. Over-tightening damages the seal and causes leaks.
Some cartridge housings have a small drain valve at the bottom. If yours does, open it before you unscrew the cap so old oil drains into a pan. Close the valve before you reinstall the cap.
Aftermarket versus dealer filters
Dealer filters carry your car manufacturer's name and cost more — typically $15 to $30 depending on the model. Aftermarket filters from brands like Fram, Mobil 1, Bosch, and Wix cost $8 to $18 and fit the same way. Both types must meet the same pressure and flow standards set by your engine's design, so either will protect your engine if you choose the correct part number.
The main difference is that dealer filters are made by the manufacturer's chosen supplier and carry the manufacturer's warranty. Aftermarket filters are made by independent companies and carry their own warranty. In practice, both last the same amount of time — until your next oil change.
Some people prefer dealer filters for peace of mind; others save money with aftermarket filters. Either choice is safe as long as you use the correct part number for your car. Buying the wrong part number — whether dealer or aftermarket — is the real risk.
How often to replace your filter
The standard practice is to replace the oil filter every time you change the oil. Your owner's manual specifies how often to change oil — typically every 3,000 to 10,000 miles depending on your car's age, engine type, and whether you use conventional or synthetic oil. When you change the oil, you change the filter.
Some newer synthetic oils and filters are rated to last longer — up to 15,000 or 20,000 miles. If your manual allows this, you can follow that schedule. However, many people change the filter at every oil change anyway because it is inexpensive and straightforward, and it removes any doubt about whether the filter is still working well.
If you drive in dusty conditions, tow a trailer, or do a lot of short trips, your filter may clog faster than the standard interval. In these cases, changing the filter more often — even if you do not change the oil — can help. Your manual may have a separate schedule for severe driving conditions.
What to do with the old filter
Used oil filters contain residual oil and should not go in the trash. Most auto parts stores that sell filters will take your old filter for free, even if you did not buy the new one from them. Some recycling centers also accept them. Call ahead to confirm they take filters before you bring one in.
If you change your own oil, drain the old filter into your oil drain pan before you remove it from the engine. Let it sit for a few minutes so the remaining oil drains out. This reduces mess when you transport it and makes recycling easier.
Frequently Asked Questions
Can I use a different brand filter than the one my dealer uses?
Yes, as long as the part number matches your car's requirements. Aftermarket filters from major brands meet the same standards as dealer filters. The key is using the correct part number for your specific vehicle, not the brand name on the box.
What if I tighten the filter too much and it leaks?
You will need to remove it and reinstall it correctly. Drain the spilled oil into a pan, unscrew the filter, wipe the sealing surface on the engine clean, and install the new filter with hand-tight plus three-quarter turn. If the leak continues, the seal may be damaged and you may need a replacement filter.
Do I need to fill a new filter with oil before installing it?
Some people do this to reduce the time it takes for oil to reach the filter after starting the engine. It is not required, but it does not hurt. If you do fill it, pour a small amount of clean oil into the filter opening, let it soak in, and repeat until the filter is about three-quarters full. Then install it normally.
How do I know if my filter is clogged?
Most cars have an oil pressure warning light on the dashboard that comes on if the filter is severely clogged and oil pressure drops. If this light comes on between oil changes, have the filter checked. You cannot see inside the filter yourself, so the warning light is your main indicator.
Can I change the filter without changing the oil?
Technically yes, but it is not recommended. The filter and oil work together — old oil is dirty and a new filter will not clean it well. Changing both at the same time is the standard practice and costs little more than changing just the filter.