Is the new OEM oil filter better?

[Mike Wevrick]

The following was posted in the oil filter sticky thread:

"A subaru mechanic told me the new filter has a check valve inside that keeps the oil from draining from the turbo cooling lines and engine internals after the car is shut off."

Despite repeated requests for confirmation of this, none have been forthcoming.

Anybody?

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[North Ursalia]

The AA060 and the AA080 both have check valves in them. The only difference in the AA080 is that it is smaller to keep it away from the crossover pipe's heat. Either filter will work. Neither will keep oil in the turbo, oil lines, and engine internals- it will drain back into the pan, like it's supposed to, for the most part. That's not what the check valve is there for.


Brian

[Mike Wevrick]

So what does the check valve do? Do aftermarket filters like PurOne have it?

[North Ursalia]

It keeps dirty oil from flowing back into the engine.


Brian

[dadswrx]

Hmmm, I always thought that check valves were there to permit oil to bypass the filter in the event that the filter becomes clogged. Without that bypass feature, a clogged filter would stop oil from flowing through the engine...

Or, so I thought...

Mike
02 WRX Wagon

[BryanH]

Originally posted by North Ursalia
It keeps dirty oil from flowing back into the engine.


Brian

Cmon now....you know better than that. The check valve has nothing to do with keeping oil from flowing back into the engine. Its to make sure the oil keeps flowing even if its dirty.

[hawksoob]

Question....does that check valve even matter if the filter is positioned vertically, like in many of the Subies?

[Mike Wevrick]

I don't see how the orientation of the filter would matter.

[Jon [in CT]]

Since someone has brought up Subaru oil filters again, I noticed a little blurb on p. 3 of this SOA article:

Oil Filters: H-4 Versus H-6 Engines

Subaru H-4 engines come from the factory with an OEM P/N 15208AA060 oil filter. The same part number is used for replacement. H-6 engines come with an OEM P/N 15208AA031, and S0A5165109 is used as a replacement.

Both filters have the same physical dimensions as far as threads, O-ring, and bypass valve opening pressure (23 p.s.i.) are concerned. However, the H-4 filter has 141 square inches of filtration surface, while the H-6 filter has 201 square inches of filtration surface.

The H-4 filter should not be used on the H-6 engine. Using the H-4 filter may cause it to become contaminated faster and allow the bypass valve to open, allowing unfiltered oil to circulate through the engine.

So why wouldn't a filter with 43% more filtration surface area also be good for an EJ20, like it is for the EZ30?

[hawksoob]

Originally posted by Mike Wevrick
I don't see how the orientation of the filter would matter.

If it's positioned vertically, the oil couldn't drain back; it would stay in the filter. Then again, that is under the provision that the valve was to keep that from happening, which was pointed out above not to be the case.

Oh well....

[rao]

Originally posted by Jon [in CT]
So why wouldn't a filter with 43% more filtration surface area also be good for an EJ20, like it is for the EZ30?

Because the H6 has a higher volume oil pump so the filter with more survafe area may cause a drop in the oil pressure, or cause the pressure overide valve to open (it could act as if the filter was blocked) and cause the oil to bypass the filter completely.

It is much more of a theoretical than a practical concern. If the filter is changed according to the specs, it unlikekly to cause any problem, jsut as it is iunlikely to make any difference what type of filter is used if it is changed when it should be.