How often do bypass happen.

[Hamster]

Out of curiosity, assuming we follow factory recommendations on oci, filter and oil. How often do oil filters go into bypass?

For instance, I have and Ford 5.0, I follow the OLM, Use Motorcraft FL-500S and MC Synblend 5W-20 per user manual. Does the filter go into bypass at all during its service life if I do what the factory consider normal duty driving? Or does it go into bypass every time I start the engine? Or accelerate on the freeway when the RPMs goes up?

 

[Eddie]

I have never seen any data on this and only guesses. My guess is that the filter only goes into by-pass on very cold days and that depends on the engines oil pumping system.

 

[CATERHAM]

Every time an engine is started the filter by-pass can open due to the momentary pressure differential.
That's why with engines that have the filter by-pass in the filter I much prefer the by-pass at the top of the filter can and not at the bottom. Motorcraft, M1 and WIX to name three are designed that way but many aren't so that any crud at the bottom of the filter can be drawn into the engine.

 

[ZeeOSix]

There are some other threads talking about the same subject matter.
Click Here

Do a search for member Jim Allen's posts. He put a delta-p gauge and a data acquisition system on his truck to capture the filter delta-p and bypassing in real life use situations. His conclusion was the bypass valve rarely opens in normal driving situations.

Now of course if you fired up the engine at 10 deg F and revved the engine to 4000 RPM the filter will most likely go into bypass. Or if you never changed the filter and it clogged up then of course it will start going into bypass.

Change the oil and filter as required, and warm up the oil before going crazy with the RPM and the bypass valve will probably never or very rarely open.

 

[901Memphis]

Some answers to your question

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3067617/1

 

[yvon_la]

bypass happen at filter pressure ,since filter usually are set from 14 to 28 normally I suspect most of them are always on bypass since car oil pump pressure are way higher then this and oil isn't compressible.

 

[Clevy]

Originally Posted By: yvon_la
bypass happen at filter pressure ,since filter usually are set from 14 to 28 normally I suspect most of them are always on bypass since car oil pump pressure are way higher then this and oil isn't compressible.



Ummmm no.

I suggest you have a real good look at Jim Allen's data and learn something.

 

[ZeeOSix]

Originally Posted By: yvon_la
bypass happen at filter pressure ,since filter usually are set from 14 to 28 normally I suspect most of them are always on bypass since car oil pump pressure are way higher then this and oil isn't compressible.


Delta pressure across the filter media is not the same thing as the oil pressure you see on the car's dashboard. If what you think is true, then filters would be in bypass most of the time, and that's just not true.

Go read this tread to understand Delta-P, or also know as PSID (PSI Differential) across an oil filter when oil flows through it. The delta-p could only be 2~5 PSI while the oil pressure to the engine could be at 60~80 PSI. The two pressures are not the same as you think.

Filter Flow vs PSID

 

[Sayjac]

Not often, and only very briefly when it does.

 

[yvon_la]

so only the difference is relevant for bypass?ok my bad!so this mean say you have a 60 psi oil pressure (just a random number)you would need 74 psi or more f oil pressure to get the bypass to open?(again never mind the actual number since it will vary depending on your own vehicule etc)
ty for correcting me,i was under the wrong impression!

 

[ZeeOSix]

Originally Posted By: yvon_la
so only the difference is relevant for bypass?ok my bad!so this mean say you have a 60 psi oil pressure (just a random number)you would need 74 psi or more f oil pressure to get the bypass to open?(again never mind the actual number since it will vary depending on your own vehicule etc)
ty for correcting me,i was under the wrong impression!


No, the delta-pressure across the oil filter depends on the oil flow volume going through the filter, the oil viscosity and the resistance of the media.

An oil filter might only have 2 PSI delta-p when the engine has 100 PSI of oil pressure. Or, an oil filter might have 10 PSI delta-p when the engine only has 50 PSI of oil pressure. It all depends on the engine and oiling system design, oil pump volumetric output vs engine RPM, oil viscosity, flow resistance of the filter's media, etc.

With a positive displacement oil pump, the higher the engine RPM the more volume of oil is leaving the oil pump. So obviously the delta-p across the oil filter will be greatest when the engine RPM is highest, and also when the oil viscosity is the highest (ie, thick oil). That's why if you fired up the engine at 10 deg F with thick cold oil and smashed the throttle down to get 4,000 RPM or above, the bypass valve will certainly open up.

It is almost impossible to make the filter bypass valve open up even at engine red line when the oil is fully hot (200+ deg F) unless of course the oil filter is very clogged up.

 

[kbmag1]

Originally Posted By: CATERHAM
Every time an engine is started the filter by-pass can open due to the momentary pressure differential.
That's why with engines that have the filter by-pass in the filter I much prefer the by-pass at the top of the filter can and not at the bottom. Motorcraft, M1 and WIX to name three are designed that way but many aren't so that any crud at the bottom of the filter can be drawn into the engine.

Very good to know. I also have a 5.0 coyote and started looking for options of oil filters that have the by pass at the filter top like Motorcraft. Any other then M1 and Wix? FRPP (any issue of a FRPP 820)? Looking for synthetic or at least synthetic blend. Thanks, wealth of information here.

 

[CATERHAM]

I would think there must be other brands that have the preferred by-pass location but I don't know of any.

 

[KCJeep]

Originally Posted By: kbmag1
Originally Posted By: CATERHAM
Every time an engine is started the filter by-pass can open due to the momentary pressure differential.
That's why with engines that have the filter by-pass in the filter I much prefer the by-pass at the top of the filter can and not at the bottom. Motorcraft, M1 and WIX to name three are designed that way but many aren't so that any crud at the bottom of the filter can be drawn into the engine.

Very good to know. I also have a 5.0 coyote and started looking for options of oil filters that have the by pass at the filter top like Motorcraft. Any other then M1 and Wix? FRPP (any issue of a FRPP 820)? Looking for synthetic or at least synthetic blend. Thanks, wealth of information here.


Napa Gold is a Wix with a thread end bypass also.

 

[dnewton3]

Jim's data experiment is here:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3198452/1

Pretty much shows that the bypass rarely ever opens, and even when it does, it's not for long.

If you run thick oil, in the winter in the Yukon, and peg it at WOT at start-up, then it might be of issue. But if you run your OEM system as specified, it's a moot point.

And, even if it were to open, I'd again remind everyone that the wear numbers of most any typical engine show it to be a non-issue. There can only be one of two potential answers here:
1) the bypass rarely opens, and so worry is silly. The event does not happen with enough frequency to make any long term difference in wear.
2) the bypass opens all the time, but wear is unaffected anyway

Either way, it really does not matter. Wear data in most any of today's engines is super low. The effect of bypass, whether often or not, does not manifest into wear. So why worry about it?

The bypass is there to protect the filter media from deformation and destruction. That, in a secondary manner, protects the engine from blown media going downstream. The filter bypass rarely has to do it's job, and when it does, it will typically burp the fluid for a short second or less, and then it's back to normal.

 

[OneEyeJack]

I used to design and build emergency generator sets for extreme weather. We long ago instrumented one for various reasons and with good multigrade oil only saw a spike in pressure high enough to trip the bp valve in dead cold startups at temps well below zero. The spikes were of short duration and good luck figuring out if it made and difference in wear other than saving the oil system from a blow out. I can't imagine anyone on this board that would run an engine without an oil change long enough to discover how the bp valve works.