When the oil is cold, like really cold, and thick it will bypass the filter because the pressure is to high, that helps with dry starts and builds oil pressure faster.
Now think of the small holes in the filter, and the thick oil, and the high relief pressure of the filter...
Now, the oil pump itself has a relief valve, so if the filter becomes clogged or the oil is to thick at start up it will bypass the filter.
So which relief valve do you worry about? The one build into the engine or the one on the oil filter?
Personally, I dont worry about either, I use the oil filter I use and it works for me.
I would use this huge mammoth oil filter if I was about to embark on a 15,000 mile trip and I filled the engine full of Royal Purple 15w-40 and I knew I was not going to be changing the oil for at least 15,000 miles.
But for the 5,000 mile oil changes that I do, I think a quality normal sized oil filter works just fine.
On my route is a place that sells Mann oil filters and I will buy one next time, but it wont be the huge manly one.

 

I guess the downside is that with 25 - 50% more oil pressure you'll leak 25 - 50% more oil - or more.

 

Scooped one up for 6.95 at pep boys and will probably throw it on in a week or two since I'm still about 400 miles from my next oil change. I'll report back then if some life altering inciden occurs due to it's instalation.

 

From taking apart the filter and trying to reverse engineer the setup, I think it works like this.
The engine oil pump has a filter bypass set at like 80? psi to protect the pump. So WE don't have to worry about the pump on our trucks.

The filter may have a bypass so worse comes to worse, you can still pass oil pressure through it (at 36 LBS) no matter what. (This may also be a safety for vehicles/engines with no other bypass?)

Or It may be the filters known capacity. IE "this filter can filter up to 36 PSI of whatever weight oil, then we have to open the bypass or we lose flow"

I'm leaning towards the fact that the filter is so much larger, has so much more surface area, and is made of the highest quality stuff that the engineers were able to increase the bypass pressure to 36 PSI with no ill effects.

The strange thing is, with a larger filtering surface area, less pressure is required to push the same amount of oil through the filter element due to the molecules moving slower (like blowing through a straw hard vs blowing through a straw soft) This would lead me to believe they could LOWER the bypass pressure and retain the same characteristics. So maybe the bypass in the filter is to protect the filter element itself, and has nothing to do with engine/oil/flow/pressures at all?

 

On the MANN site, they have two versions of this filter, the /4 at 36 PSI, and the /7 at 10 PSI. Sorta like a Chevy - crank it up and oil PSI goes to like 60+, because it is in bypass, then as oil warms it drops back to normal. My old Merc does the same thing, 3+ bar at idle cold, down to 1.5 bar hot. But at least we have factory oil gauge, guess Rover was worried about Nervous Nellie bringing it in for warranty service because the gauge didn't drop when they were a quart low...

 

I've used the WIX 51773 which is 6.982" tall with a 3.663" diameter and there was plenty of clearance. That's a little smaller than the Purolator/MANN, but I don't recall thinking, "Wow, this is a tight fit."

The only clearance issue is if you have a relocated steering damper, then the filter won't fit.

 

Here's pix from my D1. The white filter is a WIX 51459, I also show other filters (WIX 51515, Bosch 72198) that have been used on my truck, the little Bosch came on it and was mangled to get off. Does not seem to be a clearance problem. I like low price, big, extra oil capacity, low filter "pressure loss", etc. IMHO one of the ways to long life is good oil, good filter, and change early and often. The idea of running a small capacity oil system, with a midget filter, at higher temps, and for 15,000 - 25,000 miles oil changes is a great way to sell more vehicles. The more expensive oil and filters are better, but they lull owners into deferring maintenance because of the price. Your engine produces "X" dirt in the oil per hour. So if you run extended drain interval oil, and your midget super filter gets clogged up, it will bypass, and your engine is then lubed by unfiltered expensive oil for the rest of the 25,000 miles you were planning on driving on that oil change. Rant over.

Our international members may find the MANN 950/4, Purolator stickers it in US as L40316, box made in Mexico, but filter made in Germany.

 

I was talking to my Audi mechanic (friend) and asked him about the oil pressure relief valves in oil filters. He told me that he has always tried to use the lowest pressure (close to oem spec) instead of filters with a higher psi relief valve since you don't want the pump bypass to work harder.

I guess I bring this up as I am not sure if his logic makes sense?

With his logic it seems like the '7' version at 10 psi would be more appropriate then the '4' version?

 

Just ordered one of these filters from advance auto parts, will arrive tomorrow, they didn't have it in stock. I am also waiting for a filter housing O-ring, where my car is leaking. i wanted to wait until the next oil change, but will just swap the filter atthe same time.
I do not want to change the oil, since I have only less than 500 miles on the oil, but can some body tell me how much oil is usually lost by changing the filter/opening the filter housing?

 

You'll need about a quart or just a little more to fill the new filter. Not much is lost, put you will need a pan, it is more than a paper towel will grab.