I'm sure this has been beaten to death, but I want to ask anyway. According to Mann, the stock filter has a 2.5bar (36psi) differential oil pressure setting. Most of the filters recommended by guys on this site (Napa 1516, Wix, Motorcraft FL1-A, etc.) have bypass settings well below that (around 8-16psi).

Does anyone know why VM would specify a bypass setting so high? Are the Beta ratios much higher with the Mann filter? I've read on BITOG that some other VM motors are rated high as well.

What are the repercussions of running a lower setting? Dirtier oil circulating?

I think the bypass setting is more related to the size of the filter.
For example, the FL-1A is a larger filter that will have a lower internal pressure than the stock filter that is smaller.
A larger filter has less resistance to flow than a smaller filter.

Either way, its good reminder about regular oil changes.

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U.S. Army Retired

This same thing was an issue on the Subaru 2.5L motors. A lot of the aftermarket filters had a much lower bypass setting than the OEM filters, and Wix/Napa were the only filters which matched the subaru spec. It may have to do with the pressure at which our pumps run at. The Subarus had a fairly high pressure oil pump and therefore the filters needed a higher bypass to match.

It may also have to do with the filter media durability. Maybe Mann thinks their filters are stronger and can handle a higher pressure differential across the media.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

Just guessing but it may be that VM expected the oil to get very dirty very quickly due to soot loading so they chose a filter that would not start to bypass within the first few hundred miles. With no EGR I don't expect the filter to clog to nearly the same degree so a lower bypass pressure will suffice.

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There is a good write up on BITOG about the filter bypass.
Basically, regardless of the type of filter and bypass pressure setting, there are times during normal operation that the filter bypass will open. Such as:
1. when cold thick oil is being pushed through at engine startup.
2. during moments of rapid high acceleration.
In any case, those moments are relatively brief and the bypass only opens just enough to maintain good flow. The majority of the oil still passes through the filter.

I've been running the larger FL-1A type filters since I've bought mine. At 160,000 miles when I pulled my head off, the rocker arms were still in good shape. Although the true test would be to inspect the rod and main bearings since they are first in line for receiving oil.
And yes, my EGR valve has been disabled by one means or another for most of its life.

And just as a reminder.
Oil pressure is the only thing keeping the crankshaft journals from contacting the bearing surface.

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U.S. Army Retired

I think you answer your question. As I remember, the oil weight mentioned by vm is lowest 5w30 and highest 15w40. I would always choose a higher bypass since this ensures more flow through the filter media. And I will always choose the thinnest oil available, that won't break my wallet, since the thinnest oil produces the lowest pressure, thus more flow through the filter media. But best safest thing is to have some oil analysis to ensure the optimum oil change interval per your oil choice, at the end the psi war has less significance provided you have a good engine and run with a good oil and oil filter brand.

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.

The oil pressure is going to be directly related to engine RPM so unless your driving around at 4000 rpms all day i dont think you are going to end up bypassing any filter more than 5% of the time. And if your engines cold, don't be a wack job and hammer on it.

If you have oil flowing through the filter most of the time, then all the contaminants are going to be filtered out. Its not like for the 10 seconds that you are in bypass that a whole plug of metal shards is going to come rolling through.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs