Interesting. The MANN 950/4 has a bypass valve pressure of 2.5 bars or 36.2 PSI. My PSI drops below the range of 50 is when it's very hot and sitting at idle, it'll drop to 28. So you're saying I'm bypassing the oil filter while sitting at a stoplight?

 

The oil pressure is supposed to drop at idle when warmed up. That is because (among other things) that the bypass valve has closed off and fluid is being pushed through the media. You'll notice the change when you crank up cold in the morning, idle PSI will be high until oil warms up and valve closes back. You'll also see it at wide open throttle (if you were inside the filter). Other boards with engine tuners bemoan the lower PSI bypasses sending unfiltered oil to their turbos under moderate acceleration.

The purpose of the oil filter bypass valve is to keep the engine from starving for oil if filter becomes clogged. So you have to have a pressure differential across the filter of that much to open the valve. The higher PSI means the filter will try to keep cleaning oil longer than stock one. It sure is bigger, and has more media.

But if you treat the truck like many previous owners, oil change at 25,000 whether you need it or not, even that big honkin' filter could get plugged up.


Just my opinion, you can count on others.

 

The bypass doesn't just come in to play when the filter is clogged. Also when you have a high pressure differential at cold start (or any other time). Higher valve setting, as I mentioned in a previous post means you can have oil starvation for a longer time, before the valve opens and you get oil flow, like at cold start.
I think I'd rather have unfiltered oil than no oil going through my turbo.

 

i love that the title of this thread is: "THE END ALL ANSWER TO ......."

 

Just so I'm clear, what does the valve pressure PSI number mean? Does it open or close above or below the listed rating? The 950/4 is rated at 36 psi, mine cold starts at 52 psi idle, drops to 45 at 2k rpm cold. Drops to 28 psi at idle with engine temps near 190, and 52psi at 2k rpm hot. So when is my valve closed bypassing the filter? You're making it sound like when it's cold which would mean my filter is being bypassed at all times other than hot idle?

 

Here's my take on it. Let me preface by saying I don't claim to be an expert, but this is based on research I've done about how oil filters work.

Some people in this thread seem to think the bypass valve only matters when the filter is completely blocked. This is not the case. The bypass valve's most important job is allowing cold, thick oil to flow on start up.

The majority of engine wear happens within the first 15-20 seconds after it's started. That's when the motor is running without adequate lubrication.

It's also when the oil is thickest because it's cold, so it doesn't want to flow. With 15w40 it's very thick, so it may take even longer. This is why many people run 5w40 - it flows freer when cold, when the engine needs oil the most.

What the engine needs (in order) is #1 oil lubricating the engine and #2 for that oil to be filtered to remove debris.

So a low psi bypass valve is going to let that cold oil flow more freely when the engine needs lubrication the most. A larger filter will flow better than a smaller filter due to the increase in surface area, but still may not flow better than a smaller filter with a lower psi bypass valve.

BTW, on page 4 of this thread Antichrist says:

So even a Wix engineer agrees this filter will starve the engine of oil on startup.

Note: there is a 50 psi oil filter bypass built into the engine, but 50 psi is basically a completely blocked filter or a you've stomped on the throttle. And BTW it opens at 50psi, but how much oil can it pass? It's designed to be working in cooperation with a 8 psi bypass filter. So at WOT the engine bypass opens, but if the filter is more restricted than stock due to it's higher bypass psi, the engine is once again being starved of oil.

I would also suggest that the elevated oil pressures people are seeing with the Wix are a sign that I'm correct and the filter is restricting oil flow. This is something I think people in this thread aren't understanding. Your Glowshift sandwich pressure sensor reads pressure flowing *into* the filter, not out. So if the numbers go up with a Wix compared to a M1, that means the Wix is restricting oil flow and working your pump harder. It isn't necessarily raising the pressure of oil flowing out of the filter. Your gauge might show 28 psi hot at idle, but that Wix could have a pressure drop across the filter of 20 psi, so your outflow is 8 psi (around 6 is where the Low Oil Pressure light comes on, and it measures filter outflow pressure). We just don't know.

The only way to conclusively answer these questions is to install pressure sensors before and after the filter, then test different filters using the same brand and weight of oil. Then we'd know if the increased bypass pressure is starving the engine of oil.

If I were you, the next oil change I'd try another oil filter that captures similar sized particles (I believe the Wix filters at 35 microns, while the M1 filters at 10-12 microns) and see what your pressures read. If the pressure drops, that's telling you the higher bypass pressure was creating resistance and slowing the flow of oil thru the engine.

For that matter, I guess you could go buy a filter and spin it on right now without draining your oil. Then post your numbers so we can argue about them.

Or, in the future you could just run the filter that the manufacturer recommended and not worry about it.

 

The bypass psi value is when there is a differential pressure of that value across the filter media. For a 36 bypass setting, if it was 36 on the inlet side and 0 on the outlet it would open. But if it was 42 on the inlet side and 10 on the outlet it wouldn't open.
Someone check my work, I'm distracted at the moment.

 

That sounds correct to me, Tom.

However, one thing to remember is that 'open' isn't binary (i.e. open or closed). It starts opening when the differential pressure reaches 36 psi.

Some good info here:
How Do Oil Filters Work?

Bypassing the filter isn't a bad thing if it allows the engine to get oil it needs to lubricate.

 

Yes, like a thermostat in some respects. I agree about the benefits of bypassing the filter media, that's why we have bypass valve.

 

re: you can have oil starvation for a longer time, before the valve opens and you get oil flow, like at cold start.

IMHO the valve is a bypass, like a shunt around, not an on/off. If there was no flow of oil, you'ld have a very noisy engine when started. I would agree that unfiltered oil may be reaching the engine, but not that it is starving. My oil light goes off in moments. My PSI goes to 44.

My Cummins friends have this on their site: A by-pass valve is required in full-flow filtration to make sure that the engine gets lubrication when oil is cold or the filter is plugged.

So my point would be that the engine will get oil. I'll accept that it may be un-filtered at some points. From what I have read the lower psi bypass valves in some filters allow them to go to bypass mode more frequently during operation of the vehicle, so like every time you pull away from a light you are sending a squirt of unfiltered oil along.

BTW, nothing like oil and filters to get people posting.

And my dip stick looks a helluva lot better than the inside of my engine.... the BBQ champs have nothing on my slow roasted Rover.