What is the correct AC filter number??
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Instructor
Joined: Aug 2004
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What is the correct AC filter number??
I just bought an '85, the Owners Manual says that the AC oil filter number to use is PF25. I haven't looked under there yet to see what was used, but there is talk around here about a short type filter being used, which I also saw in a filter guide in Auto Zone. So what is correct? What do you use? 
Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Most everyone has discontinued the PF25 type filter and there is a substitute that is smaller AC Delco PF454. There are also larger filters that work.
You will have to look thru the filter catalogs to find the part number, I used a larger filter that holds even more than the PF25 did and I believe it was from a GM pickup.
You will have to look thru the filter catalogs to find the part number, I used a larger filter that holds even more than the PF25 did and I believe it was from a GM pickup.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
PF25's may have been unique to the L98 motor found in Vettes and some Camaro's and Firebirds. The smaller PF454 filter might be used in lots of other GM applications and if the filter media in the smaller filter does a good job, the it would make sense from a business view to drop the PF25 if it was a limited application in older cars.
The problem I have with the smaller filter is that the filter itself is so small that it effectively lowers the total amount of oil the engine holds. The larger filter I use holds almost 3/4 of a quart and simply adds to the total amount of oil available for the engine. The bigger filter still doesn't go below the bottom of the oil pan so it should not be in danger of getting hit by road debris. Easier to grab when changing too.
The problem I have with the smaller filter is that the filter itself is so small that it effectively lowers the total amount of oil the engine holds. The larger filter I use holds almost 3/4 of a quart and simply adds to the total amount of oil available for the engine. The bigger filter still doesn't go below the bottom of the oil pan so it should not be in danger of getting hit by road debris. Easier to grab when changing too.
