Oil filters are a critical component of any vehicle’s lubrication system. They help remove contaminants and debris from engine oil to keep your engine running smoothly.
The thread size of an oil filter matters because it must properly fit the engine to seal and function correctly.
The most common oil filter thread sizes are 3/4-16 UNF for most domestic vehicles and M20x1.5 for many imports.
Large trucks, heavy equipment, and other applications may use 1-16 UNF, 1-14 UNF, or other larger sizes.
Using the correct thread size prevents oil leaks, allows proper oil flow and filtration, and avoids engine damage.
Later sections will cover how to identify the right thread size for your vehicle, use adapters if needed, and properly install and change oil filters.
Proper oil filter selection, fitment, and maintenance helps extend engine life.
Metric Thread Sizes
Many European and Asian vehicles use metric thread sizes for their oil filters.
Some of the most common metric sizes include:
- M20x1.5 – This size is found on numerous Audi, VW, Mercedes-Benz, Volvo, Toyota, Nissan, and Honda models. Examples include the Audi A4, VW Golf, Mercedes C-Class, Volvo S60, Toyota Camry, Nissan Altima, and Honda Civic.
- M22x1.5 – Common on BMW, Mercedes-Benz, Volvo, Saab, and Subaru models like the BMW 3-Series, Mercedes E-Class, Volvo V70, Saab 9-3, and Subaru Outback.
- M24x1.5 – Used on various Audi, VW, Mercedes-Benz, Volvo, Porsche, and BMW vehicles. Examples are the Audi A6, VW Passat, Mercedes S-Class, Volvo XC90, Porsche 911, and BMW 5-Series.
- M28x1.5 – Found on some Land Rover, Jaguar, Volvo, and Chrysler models including the Land Rover Discovery, Jaguar XJ, Volvo XC60, and Chrysler 300C.
The “M” indicates a metric thread pitch in millimeters, while the two numbers separated by “x” give the thread diameter and thread pitch.
So M20x1.5 means a 20mm diameter thread with a 1.5mm pitch between threads.
Knowing the specific thread size used by your vehicle is important for selecting the correct replacement oil filter.
Consult your owner’s manual if you’re unsure of the thread measurement.
UNF Thread Sizes
UNF (Unified Fine) is the other common thread standard used for oil filters.
It is most commonly used by American and Asian vehicle manufacturers.
Some of the most common UNF thread sizes for oil filters include:
- 3/4″-16 – This is used on many Dodge, Chrysler, Jeep, Toyota, Nissan, and Honda vehicles. Examples include the Toyota Camry, Honda Accord, Nissan Altima, Jeep Wrangler, and Dodge Ram 1500.
- 13/16″-16 – GM uses this thread size on many of their V8 engines. It can be found on vehicles like the Chevy Silverado, GMC Sierra, and Cadillac Escalade.
- M22-1.5 – This metric thread size is very close to 3/4″-16 and is used on many Asian vehicles like Toyota, Lexus, Infiniti, Hyundai and Kia. The Toyota Tacoma and Lexus RX350 are examples.
- M20-1.5 – Another metric thread used by Asian manufacturers. It is approximately equal to 13/16″-16 and used on vehicles like the Honda CR-V.
The most common oil filter wrench sizes needed for UNF threaded filters are 3/4″ and 13/16″.
It’s important to identify the correct size when changing your oil filter to avoid filter housing damage. Adapters are available to convert between thread sizes if needed.
Choosing the Right Size
When selecting an oil filter, it is crucial to choose one with the correct thread size to properly fit your engine.
There are a few ways to identify the right size filter for your vehicle:
- Check your owner’s manual – The manual will specify the thread size needed for your make and model. This is the best place to find the correct size.
- Look up specs online – With the make, model, and year of your vehicle, you can search for specs on websites like AutoZone.com that list the thread size.
- Measure the threads – Use a thread gauge tool to physically measure the threads on your engine where the oil filter screws on. Compare the measurements to standard metric and UNF thread sizes.
- Match the old filter – If you still have the old oil filter, you can simply match the thread size by visually comparing it to new filters. This ensures an identical replacement.
- Consult a mechanic – Auto mechanics have access to databases and resources to look up the specific thread size needed for most vehicles. Stop by a shop and they can identify the right size.
- Contact the dealer – For unusual or proprietary thread sizes, the car dealer’s parts department will have the specifications for your exact make and model.
Carefully checking the threads and selecting the properly sized oil filter is important to avoid stripping the threads or having the filter fail to seal properly during installation.
With some basic research and measurement, you can easily determine the correct size needed.
Using Adapters
Oil filters come in a range of thread sizes, so you may need an adapter if your oil filter doesn’t match the threading of your engine’s oil filter housing.
Adapters allow you to install a filter with a different thread size.
The most common adapter situation is using an M22x1.5 or 3/4-16 thread filter in an engine that requires a 3/4-16 or M22x1.5 thread respectively. For example:
- If your engine requires a 3/4-16 thread filter but you have an M22x1.5 thread filter, you’d need a 3/4-16 to M22x1.5 adapter.
- If your engine calls for an M22x1.5 thread filter and you have a 3/4-16 thread filter, get an M22x1.5 to 3/4-16 adapter.
Another scenario is adapting larger or smaller thread sizes like M20x1.5 down to M22x1.5 or M24x1.5 up to M22x1.5.
Adapters allow flexibility if your preferred brand of filter doesn’t match your engine’s thread size.
Just be sure to get the properly sized adapter for the threads you are converting between.
Using thread adapters improperly can result in the filter not sealing correctly and leaking.
Installing the Filter
When installing a new oil filter, it’s important to follow some key steps to ensure proper installation and prevent leaks.
Here are some tips:
- Make sure the mounting surface is clean. Use a lint-free rag to wipe away any dirt, grime or old oil from the filter mounting pad. Any debris left behind can prevent a good seal.
- Apply a thin coating of new, clean oil to the filter gasket before installation. This helps the gasket slide into place and conform to the shape of the mounting surface. Do not use old oil as it may contain contaminants.
- Hand tighten the filter until the gasket makes contact with the mounting surface, then tighten about an additional 2/3 to 3/4 turn. Over tightening can cause the filter to warp or damage the gasket. Consult your vehicle owner’s manual for the proper torque specification.
- Start the engine and check for leaks. Let the engine run for at least 60 seconds to build oil pressure before revving the engine slightly. This pressurizes the system and will reveal any leaks at the filter mounting location.
- Make sure to properly dispose of the old oil filter according to your local environmental regulations. Many auto parts stores will accept used filters for recycling. Do not simply throw it in the trash.
Following these steps will help ensure a proper oil filter installation with no leaks.
Taking your time and applying the filter correctly is essential for engine protection and performance.
Don’t rush the job.
Removal and Change Intervals
Changing your oil filter regularly is an essential part of vehicle maintenance.
Most manufacturers recommend changing your oil filter every time you change your engine oil, or around every 5,000-7,500 miles.
When removing an old oil filter, it’s important to follow some basic steps:
- Run the engine for 5-10 minutes to warm up the oil. This will make it drain out of the filter more easily when removed.
- Locate the oil filter, usually near the bottom of the engine cylinder block. Refer to your owner’s manual if unsure.
- Place a container underneath to catch any dripping oil.
- Use an oil filter wrench or pliers to grip the filter. Turn it counter-clockwise to loosen.
- Once loose, unscrew the filter by hand and remove it. Allow all excess oil to drain.
- Use a clean rag to wipe off the filter mounting surface on the engine block. You want this perfectly clean for the new filter.
- Check the old filter gasket for any pieces that may have stuck to the engine. Remove any debris.
- Apply a thin layer of fresh oil to the rubber gasket on the new replacement filter. This helps it form a tight seal.
- Screw on the new filter by hand until the gasket contacts the mounting surface, then tighten about 2/3 to 3/4 turn further.
- Add new oil in the amount specified per your owner’s manual. Start the engine and check for any leaks.
- Properly dispose of the old filter, which contains used oil and other contaminants. Many auto parts stores will accept old filters for recycling.
Performing this oil filter change routinely at the vehicle manufacturer’s recommended interval helps remove damaging contaminants from the oil and ensures optimal engine protection.
Troubleshooting
Installing or changing your oil filter incorrectly can lead to some common issues.
Here are some troubleshooting tips:
Cross-threading – This happens when the oil filter is not threaded straight onto the engine block. It can damage the threads on the engine block, causing an improper seal and oil leaks. To avoid cross-threading, turn the filter by hand until you feel it engage the threads properly before tightening it. Make sure the filter is threaded on straight.
Oil leaks – If the filter’s rubber gasket does not create a proper seal, engine oil can leak out around the filter. This can happen if the old gasket was not removed before installing the new filter, creating a double gasket. Use a gasket scraper to ensure the old gasket is fully removed. Inspect the new gasket for any defects before installing. Make sure the filter is tightened to the proper torque spec.
Double gaskets – If you fail to remove the old oil filter gasket, stacking another gasket on top can prevent the new filter from sealing correctly. Always use a gasket scraper tool to remove any remaining gasket material from the engine block before installing a new filter. Take extra care to avoid leaving behind rubber material.
Over-tightening – While the filter needs to be tightened adequately per the manufacturer’s specs, over-tightening can actually cause leaks by warping the filter or crushing the gasket. Use a torque wrench to tighten accurately to the specified torque.
If you experience leakage or see oil around the filter, remove the filter and inspect for issues.
Clean off any oil residue and replace the filter with a new one, taking care to fully remove any old gasket material.
Check the engine block threads for any damage before installing.
Brand Differences
When choosing an oil filter, the brand can make a difference in thread sizes and overall quality.
Here’s an overview of some major filter brands to consider:
Fram – Fram oil filters use standard metric M20x1.5 threads on most models. They are designed for easy installation and removal, with a gripped texture on the housing. Fram filters offer decent filtration performance for the price point.
Mobil 1 – Mobil 1 is known for high end synthetic oil and filters. Their filters have standard metric threads in most sizes. The focus is on advanced synthetic media for premium filtration. Expect a higher cost, but quality construction.
Purolator – Purolator oil filters are known for above average contaminant removal. Most use standard metric M20x1.5 threads, with some larger sizes using UNF threads. Overall, Purolator offers very good filtration performance across their line.
Wix – Wix oil filters are common at auto parts stores. Their spin-on filters use metric M20x1.5 threads on import vehicles, and UNF threads on domestic models. They offer efficient filtration media in a durable canister. Good performance for a moderate price point.
Bosch – Bosch filters have a reputation for precise engineering and premium materials. They utilize standard metric and UNF sizing. Expect excellent contaminant removal and longevity. Bosch filters can be more costly than average, but deliver quality.
So when choosing a filter, consider the brand’s reputation and your vehicle’s thread sizing. Higher cost filters often deliver better filtration over time. But moderately priced quality brands can suffice for many vehicles.
Conclusion
Choosing the correct oil filter thread size for your vehicle’s engine is critical to ensure a proper seal and prevent oil leaks.
While it may seem harmless to try and improvise with the wrong size filter or adapters, this risks causing serious engine damage over time.
Oil leaks can lead to insufficient oil pressure and lubrication, resulting in premature wear, overheating, and even complete engine failure if left unaddressed.
The thread specifications are engineered precisely based on the vehicle’s make, model, and engine design.
While aftermarket filter brands may vary in quality and features, they must adhere to the correct sizing standard or they simply won’t fit and seal properly.
Don’t take shortcuts when it comes to something as fundamental as the oil filter.
Consult your owner’s manual or an online database to lookup the correct size.
Purchase the proper filter or adapters for your vehicle.
Take time on each oil change to carefully examine the sealing surface and ensure everything is threaded on straight.
Following these best practices will help your engine operate smoothly for years to come.
