Originally Posted by geeman789
Let me summarize for you ...
For turbo's, the higher by-pass setting MIGHT matter, in a poorly maintained engine, where the turbo screen bolts MIGHT get clogged, if there were too many by-pass events with REALLY dirty oil and filter. MAYBE.
In a non-turbo engine, it won't make any difference.
That being said, the WIX 7055's are well built, and have the " correct " by-pass setting. They work, and you don't need to stress about the Subaru by-pass spec.
Huh!?
If the turbo screen clogs, it will increase ALL upstream pressure, meaning there won't be ANY appreciable change in differential pressure across the filter.
The dP across the filter is based on the flow rate of oil (engine/oil pump speed), the viscosity of the oil and the makeup of the filter.
Take-away: keep the engine RPM low at cold oil temps.
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OP, after running Subaru OE filter almost exclusively in my previous '06 WRX and '08 STI I gave up. I've been running Fram Ultra (previously Extended Guard) filters exclusively for a long time now, for the following reasons: