What is the thread size on an oil filter?
Oil filters do not share a universal thread size. The correct size depends on the engine and the manufacturer. The most commonly met sizes are 3/4-16 UNF (a standard in many US-made engines) and metric sizes such as M20x1.5 or M22x1.5, though other specifications do exist for certain models.
In practice, the thread size is defined by the engine’s oil filter mounting and the corresponding filter nipple. Using the wrong size can cause poor sealing, leaks, or improper oil flow, so verifying the exact specification for your vehicle is essential before purchasing a replacement.
Understanding why thread sizes vary
The thread on an oil filter mounting is part of a standardized interface between the engine and the filter. While many engines use a familiar standard, manufacturers sometimes choose different sizes to fit specific design constraints, regional manufacturing practices, or supplier availability. As a result, you’ll encounter both imperial (inch-based) and metric thread sizes across different makes and generations.
Common thread sizes you may encounter
Here are the thread sizes you’re most likely to see on consumer vehicles. The list reflects the sizes that appear most often in service catalogs and customer vehicles.
- 3/4-16 UNF — A widely used imperial thread size found on many US-made engines and a large portion of older and newer mainstream models.
- M20 × 1.5 — A common metric size used on many European and some Japanese/Asian vehicles.
- M22 × 1.5 — Another metric option encountered on certain European makes and some later-model vehicles.
Note: Within each category, there can be variations in gasket size, filter diameter, and overall length. Always verify against the specific vehicle’s service information or the replacement filter’s compatibility guide.
How to confirm the correct size for your vehicle
To ensure you choose the right thread size for your oil filter, use these steps to verify before purchasing or installing a new filter.
- Check the owner’s manual or service manual for the recommended oil filter specification and thread size.
- Look up the OEM part number for your engine using the vehicle’s VIN or model and cross-check it with a parts catalog (OEM, Bosch/Wix/Mann, or dealer resources).
- Remove the old filter and measure the threaded portion’s diameter with calipers, and determine pitch or count threads per inch to confirm whether it’s 3/4-16 UNF, M20x1.5, or M22x1.5.
- Compare your measurements with the sizes listed by reputable filter manufacturers and ensure the gasket diameter and mounting surface will align.
- If you’re uncertain, consult a mechanic or parts counter with the vehicle’s year, make, model, and engine code to avoid compatibility issues.
Verifying the exact specification helps prevent leaks and ensures proper lubrication, which is vital for engine health.
Practical tips for selecting and installing an oil filter
Beyond thread size, a few practical practices improve reliability and performance when replacing an oil filter.
- Always install a new gasket or O-ring and prime a new filter if required by the design. Not doing so can cause leaks.
- Apply a light coating of clean oil to the gasket before installation to improve sealing and make removal easier next time.
- Torque the filter to the manufacturer's specification. Over- or under-tightening can cause leaks or mounting damage.
- Clean the mounting surface thoroughly and inspect for damage or old gasket remnants before installing the new filter.
- Keep a record of the replacement part number and cross-reference it with your vehicle’s service history for future maintenance.
Following these tips minimizes downtime and helps ensure the engine remains properly lubricated during service intervals.
Summary
There isn’t a universal thread size for oil filters; the correct size depends on your engine. The three most common sizes found in everyday vehicles are 3/4-16 UNF, M20×1.5, and M22×1.5, but other specifications exist. Always verify the exact size using the vehicle’s manuals, OEM part catalogs, or by inspecting the existing filter to avoid leaks and ensure proper fitment. When in doubt, consult a professional with your vehicle’s details.
