Posts Tagged ‘maintenance’

To prefill oil filters or not?

November 9, 2009 Leave a comment

There was a comment about oil changes in a forum on

If you’re interested in compact tractors then the forums on are a great resource.


A fellow’s tractor has a horizontally mounted, spin-on oil filter in a tight spot so he is unable to prefill it.

The question was what harm there was in having no oil pressure for a few seconds while the filter filled up and I wanted to re-post and add to the comment I made there:

Regarding the pre-filling of oil filters:

I guess it depends on what you’re taught. The first mechanic I ever worked for insisted that all filters be pre-filled without exception; I never ran into a horizontal one while working for him.

While I didn’t think that a few seconds without proper oil pressure at idle with no load was a big deal(considering there’s still a film of oil on the bearings anyway), he was the boss and it became a habit

Most mechanics I know don’t and one good friend says I’m wasting my time. He’s an automotive mechanic and I’m inclined to agree with him when it comes to smaller filters he deals with but most of ones in our shop held 3-4 litres of oil.

By the way: I don’t recall running into a horizontally mounted filter larger than a demitasse.

As for the real damage that may or may not be done by not pre-filling filters:

I’m sure if you invested some time in doing some digging, you might find a paper on the subject; maybe the SAE, the other SAE, in maintenance engineering journals or the ASME Tribology Division. It might make for interesting reading but I’ll bet what you find has as much practical value as knowing how many angels can sit on the head of a pin.


Can you trust that the engineers who designed your engine considered the issue of being unable to pre-fill the oil filter and decided that it wasn’t going to be a problem? If not, then ask your local dealer what they do.

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