The simplest rule is to replace the oil filter every time you change the oil. The filter is inexpensive compared with the engine it protects, and putting fresh oil through a clogged, old filter undercuts the point of the service.
The short answer
For most cars, change the oil filter at each oil change. If your car goes a year or more between oil changes, the filter is replaced when the oil is. Your owner’s manual may list specific guidance, so check it first.
What the oil filter does
As oil circulates, it picks up dirt, tiny metal particles, and combustion byproducts. The filter traps these so they do not keep circulating through the engine. Over time the filter fills up and works less well.
Most filters also have a bypass valve. If the filter becomes badly clogged, the valve can open so oil keeps flowing, but that oil is then not being filtered. This is a reason not to leave a filter in place too long.
Why change it every time
- Fresh oil should not run through a loaded filter. An old filter is already holding contaminants.
- It is a low-cost part. Filters typically cost far less than the oil change itself in most cases, and the labor is already being done.
- It protects the engine. Clean oil and a working filter go together.
Can you change oil without changing the filter?
Technically you can, and some shops will do it on request. A noticeable amount of old oil also stays in the filter and the engine passages, so skipping the filter leaves some used oil and contaminants in the system. For that reason it is generally not recommended. Similarly, reusing an old filter is not a good idea, because filters are designed as single-use parts.
Extended-life oil and filters
Cars that go longer between oil changes, such as those using full synthetic oil, often need a filter that can last as long. Some manufacturers and brands offer extended-life filters rated for longer intervals. If you stretch the oil interval, use a filter that matches the rating and check that it fits your manual’s recommendation. Even then, replacing the filter at every oil change is a common best practice. For intervals by oil type, see how often to change your oil.
Types of oil filters
- Spin-on filters. A metal canister that unscrews and is replaced as a whole.
- Cartridge filters. A replaceable filter element inside a reusable housing, common on many newer engines. These usually come with new seals or an O-ring.
Which kind you have depends on your vehicle.
Choosing the right filter
Use a filter that is listed for your make, model, and engine. Fit, thread size, and flow characteristics matter, so avoid guessing. Your manual, the parts store lookup, or your mechanic can confirm the right one. A filter from a reputable brand that meets the specifications is generally fine.
Related reading
- Oil Changes 101 explains what the full service involves.
- Synthetic vs. conventional oil can help you decide on oil type and filter pairing.