oil filter flow percentage

[DrDusty86]

Just how much oil actually flows through the filter in an automotive setup? I always thought all the oil flowed through the filter, unless it was heavily loaded and went into bypass. I have heard from several people recently that the filter only filters 20-30% of the oil, the rest of the time it's in bypass.
Thanks,
Dusty

 

[bepperb]

Gary Allen did some experiments with this awhile ago.

Filters are very seldom in bypass and usually filtering 100% of the oil. The bypass is a failsafe for a clogged filter and cold starts.

https://bobistheoilguy.com/forums/threads/how-to-test-opening-psi-for-oil-filter-bypass.110238/

 

[bepperb]

This is a sum of what Gary had to say on the subject:

"
Nope. Outside of exceptional circumstances, the filter will mostly be undetectable in terms of PSID; through a very broad range of volumes. Now if you get your hot oil treatment going ..and get high enough volume to actually make the filter taxed for throughput potential ..then it may show itself. "

"I'd restate that as being "at high enough volume". The vast majority of elevated PSID instances are when the oil pump is in relief. Again, if the volume is high enough, you can tax the throughput potential of the filter ..and ONLY then will there be an elevated PSID that can even approach the instances of cold operation oil pump relief induced PSID."

 

[LeakySeals]

Is there a list somewhere that compares oil filter bypass PSI ratings?

 

[QuadDriver]

I have responded to this question so many times over so many decades on so many forums you would think by now it would be as common knowledge as jingle bells....

There are at minimum 3 oil bypasses in your engine:

1) the oil pump itself
2) the spin on oil filter adaptor
3) the filter itself

In the beginnning, about the time adam was munching on apples, engines had a screen to catch big chunks, change intervals were 2K miles and whenther or not the nazis would land on long island was the big topic of the day.

Afterwards, (mostly full flow) sock style filters were used but they only allowed 90-95% of the oil to be filtered before it went to metal.

spin ons, dont care who makes em, dont care what they have in them, dont care about the media, only flow at best 30-35% of the oil pumped, and **0%** when cold. read that again over and over until you understand it.

no amount of web posts, no amount of tests not testing the engine, no amount of advertising will EVER change that. period. last word.

wanna get laughed at by a manufacturer or engine builder? state or imply that your spin-on filters all the oil first pass.

the liftoff pressure of the oil applicance btw is 14-15%. IT does not require to much physics to ballpark the percentage of oil bypassed if your oil pressure gauge reads 40psi.

why is there so much misunderstanding about the internals of our motors?

prolly for the same reason people vote for politicians who think that corporate tax increases end recessions, people think mcdonalds is edible food and people dont know even the firing order of their motor: no one really cares enuf to learn. and why should they? this is the disposable internet content at your fingertips age. almost 70% of internet traffic is netflix so unless the movies being streamed are 'how to build your motor, with debbie, in dallas", no one is learning anything.

I quote the late great john lingenfelter (or as best as I can quote him from memory after all 15 years has passed since the quote was heard): "you can tap and plug the oil bypass circuit in any pump and direct all oil thru the spin on. Of course this will burst the spin on so no one would actually do this right? right?"

personally, after god knows how many years dealing with these things, my oil bypass rate thru the filter is the last thing I think of. (truth be told I spend comparable amount of time worrying about the brand of oil I dump in as well. Its just so much of a non-issue. If you want it to be an issue, hop in the wayback machine and travel to the 30's)

as far as I am concerned, these matters were settled long before most - if not all - of us reading, were born.

of bigger issue, would be the effect of oxygenated fuels on the environment (and our wallets), but the oil makers have better ad men. 'increased valve lift in a can' we call it. (yes, we are being facetious)

 

[LoneRanger]

Originally Posted By: QuadDriver
'how to build your motor, with debbie, in dallas", no one is learning anything.


I may have seen that movie.

 

[OVERKILL]

Originally Posted By: QuadDriver

the liftoff pressure of the oil applicance btw is 14-15%. IT does not require to much physics to ballpark the percentage of oil bypassed if your oil pressure gauge reads 40psi.

why is there so much misunderstanding about the internals of our motors?


Well for one, the engine is a bigger restriction than the filter media once the oil is hot.


Quote:
I quote the late great john lingenfelter (or as best as I can quote him from memory after all 15 years has passed since the quote was heard): "you can tap and plug the oil bypass circuit in any pump and direct all oil thru the spin on. Of course this will burst the spin on so no one would actually do this right? right?"



Yes, but the bypass is BEFORE the filter and part of the pump assembly itself......

I can remove the blow-off on my air compressor and run it until the tank explodes, but that has no real bearing on whether all the air coming OUT of the tank is running through the air/water separator or not.

The oil being bypassed out the side of the pump is of course not being filtered. But it isn't going through the engine either.

 

[QuadDriver]

Originally Posted By: OVERK1LL
Yes, but the bypass is BEFORE the filter and part of the pump assembly itself......

I can remove the blow-off on my air compressor and run it until the tank explodes, but that has no real bearing on whether all the air coming OUT of the tank is running through the air/water separator or not.

The oil being bypassed out the side of the pump is of course not being filtered. But it isn't going through the engine either.


while there is a hi pressure bypass on your oil pump, this is quite different from the one installed at the point where your spin on oil filter attaches itself.

 

[OVERKILL]

Originally Posted By: QuadDriver
Originally Posted By: OVERK1LL
Yes, but the bypass is BEFORE the filter and part of the pump assembly itself......

I can remove the blow-off on my air compressor and run it until the tank explodes, but that has no real bearing on whether all the air coming OUT of the tank is running through the air/water separator or not.

The oil being bypassed out the side of the pump is of course not being filtered. But it isn't going through the engine either.


while there is a hi pressure bypass on your oil pump, this is quite different from the one installed at the point where your spin on oil filter attaches itself.


I'm not talking about GM engines (they have the filter bypass in the block) but rather engines like a Ford that has the bypass in the filter.

If you have resistance from the engine oil galleries (which is significant and what gives you your oil pressure; which is what activates the bypass on the pump) and the filter media is able to flow enough VOLUME to satisfy the demands being made on it (this would be with hot oil only) then the bypass on the filter is transparent.

Gary confirmed this with his testing rig. He WAS able to get the filter to bypass with cold oil. But once the oil was hot, it was VERY difficult to get the bypass in the filter to open because the media was able to flow enough hot oil volume.

 

[QuadDriver]

if the block pop-off is 15psi, then yes, the small amount of oil flowing thru the filter hot would not open the 25-30psi or so bypass in the filter.

unless he is able to recast the engine block, or do some fancy drilling and welding, he will never measure anything 'across' the oil filter

(to understand this you are going to have to visualize or draw out the oil circuit - keyword - circuit)

btw - the oil bypass in the pump is there to protect not the engine or the pump or the filter. why? how is the pump driven?

 

[boxcartommie22]

when you are driving on the highway oil is always in bypass..unless you use a stainless steel mesh then its filtered all the time( in my case particles of 35u at absolute single pass)...think about it going 40+mph pushing oil into paper is a no brainer..at least to me..i agree with quaddriver.at least my restrictions are not in the oil filter.

 

[OldCowboy]

Hi Quad,

Do you have any published data you can share with us? Or do you just "know"?

 

[mechtech2]

I won't make manufacturers laugh when I use their own terminology.
That is, a full flow oil filter.
Sure, some odd conditions can still cause some bypass.

 

[OldCowboy]

Originally Posted By: boxcartommie22
when you are driving on the highway oil is always in bypass..


I don't believe it. Show me the data.

Originally Posted By: boxcartommie22
..unless you use a stainless steel mesh then its filtered all the time( in my case particles of 35u at absolute single pass)...


Yep. You're letting ALL the really abrasive stuff through. Also, your filter doesn't have a bypass, so you're oil starving the engine when it's cold.

Originally Posted By: boxcartommie22
...think about it going 40+mph pushing oil into paper is a no brainer..


This is meaningless. The oil is not going 40+ mph, the car is. My car is running between 1500-1900 rpm at all cruising speeds between 40 & 65. This is on the low pressure side of the rpm curve.

Originally Posted By: boxcartommie22
...at least my restrictions are not in the oil filter.


Once the oil gets up to operating temp.

 

[OVERKILL]

Originally Posted By: QuadDriver
if the block pop-off is 15psi, then yes, the small amount of oil flowing thru the filter hot would not open the 25-30psi or so bypass in the filter.

unless he is able to recast the engine block, or do some fancy drilling and welding, he will never measure anything 'across' the oil filter

(to understand this you are going to have to visualize or draw out the oil circuit - keyword - circuit)

btw - the oil bypass in the pump is there to protect not the engine or the pump or the filter. why? how is the pump driven?


I know the oiling circuit on the SBF QUITE well.

There is no block oil bypass on engines other than GM ones that I know of.

Regardless, the CIRCUIT (using your own words) is more restrictive than the filter.

The bypass on the PUMP is there to keep the system at a reasonable maximum pressure (in the case of an SBF, 65psi). Heavy oil and a higher bypass can licorice-stick the oil pump drive shaft in this application.

Gary's measurements were made on a Jeep I-6. This engine has no in-block pressure relief valve, it only has one in the filter, like a Ford or anything not GM. He used a remote filter adapter and put a pressure gauge before and after the filter.

What he observed was that when the relief on the pump opened/closed, that action caused a differential across the filter media that could activate the bypass.

Also, when the oil was cold, the bypass would open. This was observable with a differential between the two oil pressure readings.

Here is the oiling system on the SBF:

System pressure is regulated AT THE OIL PUMP. This means that any oil going through the engine goes THROUGH the filter. If it can't go through the media, it will go through the bypass ON THE FILTER.

HOWEVER

There is a 12psi differential pressure required to activate the bypass. This isn't total system pressure, this is DIFFERENTIAL pressure, meaning the pressure that the pump sees as back pressure from the system AFTER the filter versus the restriction the filter provides, the DIFFERENCE between those two values is our differential.

When the oil is HOT and can flow easily through the filter, the differential is VERY small (IIRC, Gary stated around 1 or 2 PSI) and NOT enough to open the bypass on the filter. When the oil is COLD and does not flow well through the media, then a large chunk of the oil goes through the bypass.

 

[QuadDriver]

I think you are lumping way way to much together. You are ignoring how many v8 (big and smalls), v6 and I4s that use an oil filter mounting appliance which of course, has a bypass in it. I notice you have a M5 in your sig. What does THAT use ;-)

Unless you have a motor which uses perhaps the only full flow non-hydraulic filter made (the FL1), you have these bypasses.

I have been unable to locate a website listing hot flow rates of anything other than hydraulic oil for filter sizes, suffice to say, to handle the 5gpm, aint no little 3387A gonna do it.

 

[OVERKILL]

Originally Posted By: QuadDriver
I think you are lumping way way to much together. You are ignoring how many v8 (big and smalls), v6 and I4s that use an oil filter mounting appliance which of course, has a bypass in it. I notice you have a M5 in your sig. What does THAT use ;-)

Unless you have a motor which uses perhaps the only full flow non-hydraulic filter made (the FL1), you have these bypasses.

I have been unable to locate a website listing hot flow rates of anything other than hydraulic oil for filter sizes, suffice to say, to handle the 5gpm, aint no little 3387A gonna do it.


Ford's Modular family, which uses the smaller FL-820S filter and a much higher volume/pressure gyrator oil pump still uses the same setup as the Windsor that I've depicted above.

And there may be engines with an in-filter bypass that are on the bypass even when the oil is at temp. With a high volume oil pump and cavernous oil galleries, I'm sure it is possible. I know Subaru spec's a much higher bypass on their own filter (18psi) than most other OEM's and that may be for a reason that is in this vein.

However, the engine that this was TESTED on, a Jeep I6, showed the results I've mentioned above. And yes, that was with a larger FL-1A filter.

You make a good point about the base-mount filter adapters. Anything with a canister would use this setup. However, it would still operate on the differential system I depicted with the Windsor engine and would be subject to the same caveats regarding oil temperature/weight and total system back pressure as to whether that differential is large enough to overcome the bypass spring or not.

 

[QuadDriver]

You do know that the FL1 (and clones) has an internal bypass release at 8-12psi right?

You will generate 8-12psi priming the oil pump with a drill.....

Like I said, he was not measuring what he thinks he was measuring.

The FL1, or better clones flow 7-9gpm MAX.

Lets assume clean, therefore 9gpm

I can prolly get you to agree that oil will flow more at 200psi, than 10psi, regardless of temp (meaning all things being equal, at 60* temp, more oil will flow at 100psi than at 10psi (its nearly linear no?) And at 220* more oil will flow at 100psi than 10psi.)

I am told by the manufacturers that the max flow rates are calculated appx 10% less psi than burst pressure, simply because they do not know what the pump will output.

If the burst pressure is 200psi, and the flow rate is 9gpm at 180psi, then at 60psi (internal bypass cutoff for a hipressure windsor pump) the flow rate is 3gpm. MAX.

the pump, will easily do 5gpm. hence, someone decades ago decided that FE, FT and windsor engines needed a 8-12psi bypass

And there is something I had hoped you would have discovered, this being an oil forum and all that....the oil circuit is a resistance, a large one, when stationary. (which is why we (engine builders) tell you to rotate the motor when priming the pump and bearings after a rebuild.)

At speed, the engine is an oil VACUUM. Going way back: the two largest imparters of heat to motor oil is a) not the squirt on the underside of the pistons and b) not the valve springs but rather c) the pump and d) the bearings.

A rotating shaft will grab the oil and accelerate it instantaneously. It has been called hydrodynamic lubrication. Even here once or twice. Contrary to mythology, oil is NOT pumped into bearing. It is pumped into at LEAST a hole, but often half a bearing worth of annular groove, and in hipo a full annular groove. the spinning metal does the rest.

This occurs in the cam and main bearings. this will suck oil from the galleries, but PALES in comparison to the rod bearings. Each and every rod bearing is rotating around the crankshaft by a distance closely related to the engine stroke. (duh)

The very fact that it is rotating and that oil has mass is literally pulling the oil out of the main bearings with a force that is proportional to the square of the RPM. since the con rods do not supply oil anywhere else other than a fillet at the top which allows a squirt (and in some hi po cases a small hole drilled in the small end to get splash on the wrist), those bearings are flat without an annular groove, otherwise they would easily starve the mains.

Given that oil gallery passages are fixed in size, and that we can determine the flow rate at a certain PSI for a certain viscosity of fluid, this is what drives the PSI requirement. EVERY SINGLE TIME YOU AND ANYONE ELSE have ever read a spec on an engine it listed PSI at RPM. Someone else has done the math for you and given you only 2 numbers to read.

To sum up, dirty oil is far far worse than no oil. the worst case scenario for a full sump is a clogged or collapsed filter media.

All, without qualifications, all engines will have a mechanical mechanism to overcome this. All severe duty engines (read: with an oil cooler or remotes) will have additional bypasses to bypass the cooler when cold, and flow oil when demand outstrips the filter.

Many (but not all filters) have an internal bypass. Cannister filters (like the one on my TDI and your M5) cannot therefore an additional bypass, 3 way in fact, is built into the engine or filter appliance. I am not going to list every vehicle and every engine. MY points were made above to illustrate that few are even trying the bare minimum to understand the happenings inside THEIR OWN engine, let alone across the industry.

As I have said here and before, that test on the 4.0 - he had no idea what he was testing (and if memory serves, does not the 4.0 have an appliance bolted on?)

And for the record, the 820/825 and similar modular filters? the bypass is around 16psi. meaning it too is ALSO always open, especially at speed, the modular engines, due the increase in bearings, have a higher flow rate requirement than the engines they replaced. The flow rate published by manufacturers is an absolute, at 220*, at a psi rating below burst. No other qualifications are given (or if they are, I have never discovered them online) listing whether the flow rate is 100% bypass, 100% media, or any combination in between

 

[OVERKILL]

Originally Posted By: QuadDriver
You do know that the FL1 (and clones) has an internal bypass release at 8-12psi right?

You will generate 8-12psi priming the oil pump with a drill.....

Like I said, he was not measuring what he thinks he was measuring.

The FL1, or better clones flow 7-9gpm MAX.

Lets assume clean, therefore 9gpm

I can prolly get you to agree that oil will flow more at 200psi, than 10psi, regardless of temp (meaning all things being equal, at 60* temp, more oil will flow at 100psi than at 10psi (its nearly linear no?) And at 220* more oil will flow at 100psi than 10psi.)

I am told by the manufacturers that the max flow rates are calculated appx 10% less psi than burst pressure, simply because they do not know what the pump will output.

If the burst pressure is 200psi, and the flow rate is 9gpm at 180psi, then at 60psi (internal bypass cutoff for a hipressure windsor pump) the flow rate is 3gpm. MAX.

the pump, will easily do 5gpm. hence, someone decades ago decided that FE, FT and windsor engines needed a 8-12psi bypass

And there is something I had hoped you would have discovered, this being an oil forum and all that....the oil circuit is a resistance, a large one, when stationary. (which is why we (engine builders) tell you to rotate the motor when priming the pump and bearings after a rebuild.)

At speed, the engine is an oil VACUUM. Going way back: the two largest imparters of heat to motor oil is a) not the squirt on the underside of the pistons and b) not the valve springs but rather c) the pump and d) the bearings.

A rotating shaft will grab the oil and accelerate it instantaneously. It has been called hydrodynamic lubrication. Even here once or twice. Contrary to mythology, oil is NOT pumped into bearing. It is pumped into at LEAST a hole, but often half a bearing worth of annular groove, and in hipo a full annular groove. the spinning metal does the rest.

This occurs in the cam and main bearings. this will suck oil from the galleries, but PALES in comparison to the rod bearings. Each and every rod bearing is rotating around the crankshaft by a distance closely related to the engine stroke. (duh)

The very fact that it is rotating and that oil has mass is literally pulling the oil out of the main bearings with a force that is proportional to the square of the RPM. since the con rods do not supply oil anywhere else other than a fillet at the top which allows a squirt (and in some hi po cases a small hole drilled in the small end to get splash on the wrist), those bearings are flat without an annular groove, otherwise they would easily starve the mains.

Given that oil gallery passages are fixed in size, and that we can determine the flow rate at a certain PSI for a certain viscosity of fluid, this is what drives the PSI requirement. EVERY SINGLE TIME YOU AND ANYONE ELSE have ever read a spec on an engine it listed PSI at RPM. Someone else has done the math for you and given you only 2 numbers to read.

To sum up, dirty oil is far far worse than no oil. the worst case scenario for a full sump is a clogged or collapsed filter media.

All, without qualifications, all engines will have a mechanical mechanism to overcome this. All severe duty engines (read: with an oil cooler or remotes) will have additional bypasses to bypass the cooler when cold, and flow oil when demand outstrips the filter.

Many (but not all filters) have an internal bypass. Cannister filters (like the one on my TDI and your M5) cannot therefore an additional bypass, 3 way in fact, is built into the engine or filter appliance. I am not going to list every vehicle and every engine. MY points were made above to illustrate that few are even trying the bare minimum to understand the happenings inside THEIR OWN engine, let alone across the industry.

As I have said here and before, that test on the 4.0 - he had no idea what he was testing (and if memory serves, does not the 4.0 have an appliance bolted on?)

And for the record, the 820/825 and similar modular filters? the bypass is around 16psi. meaning it too is ALSO always open, especially at speed, the modular engines, due the increase in bearings, have a higher flow rate requirement than the engines they replaced. The flow rate published by manufacturers is an absolute, at 220*, at a psi rating below burst. No other qualifications are given (or if they are, I have never discovered them online) listing whether the flow rate is 100% bypass, 100% media, or any combination in between


You appear to be completely lost on the concept of what a pressure differential is and subsequently, how/why the bypass opens.

I am well aware of the spec's on the FL-1A, I posted them above, and also the details of how/why the bypass operates. You appear to either not have read them or believe so strongly in your own opinion on this subject that you are unwilling to entertain the idea that the system perhaps does not operate in the manner in which you assume.

 

[bruno]

There does seem to be a basic misunderstanding of the purpose of the filter bypass - it's there to protect the engine from loss of oil flow if the filter plugs .