How to Find an Oil Filter by Sizing

by Jack Hathcoat

There are four important sizes to consider when choosing an oil filter. The most important is the filter micron size. This is a rating that designates how large a particle can be that will pass through the filter. The larger the micron rating, the smaller the particle must be before it can get through. An article in Motor Oil World outlined an oil filter study conducted by General Motors using diesel engines. This study concluded that a quality filter with a good rating improved mileage by nearly one percent. The other three sizes are thread size, filter height and filter diameter.

Step 1

Remove the oil filter and drain the oil into a catch pan. Use a ruler to measure the diameter of the screw hole on the old filter. Also, measure the filter threads with a thread gauge, according to metric or SAE (Society of Automotive Engineers) thread ratings.

Step 2

Measure the diameter of the filter. This will include the sealing area of the filter. Do not measure the rubber seal area; rather, the full width of the filter body (metric or SAE sizes).

Step 3

Measure the height of the filter. If there is room, a filter can be fitted that is taller than factory specifications. This will increase filter life and oil flow. Compare the findings with a filter chart, readily available online, and select a quality filter.

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