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Guest Message by DevFuse

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Oil filter sizing

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2 replies to this topic

#1 ettev


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Posted 25 January 2012 - 05:42 PM

Is there anywhere online that indicates what different capacity oil filters can be used for the same application? (i.e. What filter would be the same as our EA81's that might hold another few ounces of oil by virtue of being a bit longer. A Purolator #PL24457 is 4.02" long, but a Purolator #PLXXXXX is the same thread size but maybe 6.35" long). Another example is that I know my one GM car specs an AC Delco oil filter #PF47, but if I buy a PF52 I get the same basic filter only the 52 is about 2 inches longer.

Specifically, I'm looking to determine what a longer filter would be for a Purolator #PL10241.

#2 GeneralDisorder


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Posted 25 January 2012 - 05:55 PM

Larger is not better for oil filters. Takes longer for the filter media to "plateau" at it's optimum micron filtration level. Too large and that will never happen between frequent oil changes (which is common amongst folks that are also looking for "bigger" on the filter) and certain particulate sizes will never actually be filtered.

Then you have differences in bypass valve construction, anti-drain-back vs. none, and other metrics that size and thread alone will not tell you.

Too frequent on the oil changes will result in the slight alkalinity of brand new oil causing etching of bearing surfaces. New oil is alkaline to offset the acidic nature of blow-by gasses.

This is all carefully engineered and you can cause serious problems by doing arm-chair engineering of lubrication systems with rule-of-thumb guessing games and myths about filtration, etc. Better to just leave it alone - OEM filters from Subaru are inexpensive and provide excellent and correct filtration. If you want more oil capacity consider a full-flow oil cooler. That will increase capacity and cooler oil lasts longer. Cool oil and full synthetic with 5k changes will do more for your engine than anything else you can do lubrication system wise.


#3 ettev


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Posted 25 January 2012 - 06:05 PM

Wow. Great info as always Rick. Thanks.

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