Latest filter comparison.

[Nuclear_42]

None of those filters are going to have a problem with "flow". Efficiency is what matters since that is what is directly correlated to wear.

Filtering is what a filter is supposed to do.

A little bit off topic. Most Subaru call for 23 psi bypass valve. Running a fram endurance or amsoil will mean way more bypassing events in low temp start up and high revs when hot with the generic 10-18 psi settin gs. Hence my reasoning for going with the BOSS. Way less resistance decreases bypassing events even further during cold starts.

 

[ZeeOSix]

This has been a great thread so far. So I ditched my usual Amsoil filter for a Purolator BOSS 22500 for my L84 5.3L. I made the change due to the cold flow highlighted in the comparison video. I’m not too excited about the filtration efficiency but I think it’s more important in below zero temps here in MN winters. I’m also dumping my Wix filters for the BOSS on my 21 Subaru 2.5L. Low filtration resistance and 20-30 psi bypass is looking good. Am I making a good choice in choosing cold flow over 99% efficiency at 20 microns vs say an Amsoil or Fram endurance filter ?

Here's all the cold oil flow dP vs flow graphs from the three different BR testing videos. In these tests, you should only look at the dP up to around 4-5 GPM because most engines will probably have the pump hit pressure relief flowing 4-5 GPM with really cold oil. What's strange about these graphs is they should be a bit more exponential from 0 to 5 GPM before the bypass valve opens. I'm not sure if the flow meter they use is the best for that setup, but that's another discussion. There hot dP vs flow looks more like the expected exponential data curve.

The crazy oiling systems on Subarus might be a different animal, but no matter what the vehicle, the bottom line is keep engine RPM low until the oil warms up pretty good. In these cold dP vs flow tests, they aren't really too far apart up to around 5 GPM of flow. But the Wix XP/NAPA Platinum (same basic filter) and the Boss do look to have ~5 PSI lower (approx 12 vs 17 PSI) cold dP around 5 GPM.

Obviously, anyone concerned about their Subaru bypassing cold oil should be using a filter with a high bypass setting for a Subaru, and again keep the engine PRM down until the oil warms up.

 

[ZeeOSix]

Here's the hot oil dP vs flow for a group that BR tested. Those curves look the way they should - ie, exponential increase in dP vs flow. In their video they said the Fram EG and TG were "highly restrictive", but an increase of only 3 PSI at 10 GPM over the other two is no where close to being "highly restrictive". It's pretty hard for an oil filter to be "highly or too restrictive" for a positive displacement oil pump. The oiling system flow resistance is many times greater, like typically around 15 times more restrictive than any oil filter. That's why a PD oil pump is used on an engine oiling system.

 

[ZeeOSix]

^^^ Just in case ... this is for the posts above, and for any others for that matter.

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