Oil filter thread size is the diameter of the screw hole where the filter attaches to your engine

The thread size is measured in millimeters and tells you which filter will physically fit your vehicle. It is not the same as the filter's overall diameter or height — it is specifically the width of the opening where the filter screws on. Common sizes are M20 × 1.5, M22 × 1.5, and M24 × 1.5, though others exist. If you buy a filter with the wrong thread size, it will not screw onto your engine at all, and forcing it can damage both the filter and the engine's filter housing.

The thread size also includes the pitch — the distance between threads — which is why you see both numbers. M20 × 1.5 means a 20-millimeter diameter with 1.5 millimeters between each thread. Pitch matters because a filter with the right diameter but wrong pitch will not seat properly and can leak oil.

Key Takeaways

  • Your vehicle's owner manual lists the exact thread size needed, usually in the maintenance section under oil and filter specifications.
  • The filter's part number encodes the thread size, so you can cross-reference it with a parts retailer's database to confirm the size before buying.
  • If you have lost your manual, your vehicle's year, make, model, and engine size will let a parts store or mechanic look up the correct size in seconds.
  • Thread size varies between vehicles and even between engine options in the same model year, so guessing from another car is not reliable.

Finding the thread size in your owner's manual

The owner's manual is the fastest and most reliable source. Look for the maintenance schedule or specifications section — it is usually near the back. The entry for oil and filter will list the thread size, often written as M20 × 1.5 or similar. If your manual is in the car, check the glove box. If you no longer have the physical copy, you can read it free from the manufacturer's website by entering your vehicle's year, make, and model.

Some manuals also include a diagram showing where the filter is located and how to remove it, which can be helpful when you are doing the work yourself. The manual may also specify the filter's recommended brand or part number, which you can use to verify the thread size with a parts retailer.

Using your vehicle's year, make, model, and engine size

If you do not have the manual, a parts store can look up the thread size in their system. You will need to provide your vehicle's year, make, model, and engine size (usually listed as 2.0L, 3.5L, and so on). Some vehicles have multiple engine options, so the engine size matters — a 2020 Honda Accord with a 1.5L engine uses a different filter than the same model year with a 2.0L engine.

You can find your engine size on a sticker under the hood, on the engine block itself, or in your owner's manual. Many parts retailers, both online and in-store, have free lookup tools on their websites where you enter this information and see the correct filter and thread size when ready. This is also a good way to double-check before you buy.

Reading the thread size from a filter part number

Every oil filter has a part number printed on its canister. This number encodes the thread size and other specifications. Part numbers vary by manufacturer — a Fram filter's number looks different from a Mobil 1 filter's number — but you can use any part number to look up the thread size in a parts database.

Search the part number on a retailer's website or on the manufacturer's site, and the listing will show the thread size along with vehicle compatibility. This method works well if you already have a filter in hand or if you are trying to verify that a filter you found online is the right one. It also works if you have an old filter from a previous oil change and want to confirm what size you need for the next one.

Common thread sizes and which vehicles use them

M20 × 1.5 is one of the most common sizes and appears on many Japanese and European vehicles, including some Honda, Toyota, Nissan, and BMW models. M22 × 1.5 is common on larger engines and some American trucks. M24 × 1.5 shows up on larger displacement engines and some performance vehicles. Smaller sizes like M18 × 1.5 exist but are less common in modern vehicles.

Thread size does not follow a straightforward rule based on engine size or vehicle type — two vehicles of similar size can use different thread sizes. This is why looking it up for your specific vehicle is necessary rather than assuming based on another car you know. A parts store can tell you in seconds, so there is no reason to guess.

What happens if you use the wrong thread size

If the thread size is too small, the filter will not screw onto the housing at all — you will feel resistance when ready and should stop. Forcing it can strip the threads on the engine's filter housing, which is an expensive repair. If the thread size is too large, the filter may screw on partially but will not seat properly, leaving a gap where oil can leak out. This can cause the filter to come loose while driving or allow unfiltered oil to bypass the filter entirely.

Either mistake means your engine is not being protected by the filter, which can lead to engine damage over time. The correct thread size ensures a tight, leak-free seal and proper oil flow through the filter media. Spending two minutes confirming the size before you buy prevents all of these problems.

Frequently Asked Questions

Can I use a filter with a different thread size if it is close?

No. Thread sizes must match exactly, including the pitch. A filter that is off by even one millimeter will not seat correctly and will leak. There is no safe workaround — you need the exact size for your vehicle.

Does thread size change if I switch to synthetic oil?

No. The thread size is determined by your engine's filter housing, not by the type of oil you use. Synthetic and conventional oils use the same filters and thread sizes.

What if I buy a filter and the thread size is wrong?

Most retailers accept returns on unopened filters. If you opened it or installed it, contact the retailer or manufacturer — many will still help you exchange it for the correct size. Do not install a filter with the wrong thread size.

Can I find the thread size by looking at my old filter?

Yes, if you have an old filter from your vehicle. The part number on the canister will tell you the thread size when you look it up online. This is a reliable way to confirm what you need for the next change.

Do all filters with the same thread size fit all vehicles?

Thread size is necessary but not sufficient. Filters also differ in length, diameter, and flow capacity. Two filters with M20 × 1.5 threads may not both fit your vehicle. Always confirm the full part number or vehicle compatibility, not just the thread size.