Filter Efficiency vs Viscosity

[Michael_P]

The other day I had an MRI done (everything was fine), so I had some time to kill in the tube. Since I was in a canister like object, I immediately started thinking about oil filters for the next 1/2 hour. Even though I stick mostly to OE recommendations, some questions popped up in my mind. I went home to search these questions and came up answerless.
Could a filter with greater efficiency be suited better for a thicker oil? Conversely; Would a thinner oil / lower efficiency filter work better than a thicker oil and a lower efficieny filter? After all, viscosity is resistance to flow. Given a few variables such as filter size, efficiency and bypass valve ratings, could there be a better match of filter based on the thickness of oil? I know many people here use oversize filters, but wold they consider a different VI oil as a result of a larger filter or a bypass filter?

 

[Quattro Pete]

Originally Posted By: Michael_P
Could a filter with greater efficiency be suited better for a thicker oil?

If anything, it should be the other way around, IMO, since a filter with greater efficiency is more restrictive.

 

[ZeeOSix]

Well obviously, as the oil viscosity goes up while keeping all other variables constant, the delta-p across the filter will increase. The largest difference in viscosity between two weights of oil would be with cold oil as apposed to hot oil.

The goal is to not create more delta-p across the media than what the bypass valve is set to crack open at. As you eluded to, there are many variables that create the delta-p. The combination of these variables will determine the delta-p seen across the filter at any given moment in time.

1) Oil viscosity
2) Oil flow rate through the filter from the pump
3) Filter media flow resistance
4) Total media area

Make the combination of these 4 variables result in the delta-p always below the bypass valve setting and you'll be "golden".

 

[ZeeOSix]

Originally Posted By: Quattro Pete
Originally Posted By: Michael_P
Could a filter with greater efficiency be suited better for a thicker oil?

If anything, it should be the other way around, IMO, since a filter with greater efficiency is more restrictive.


Depends on the other variables involved, as listed in my post above.

 

[Barkleymut]

Funny how that is the same kind of stuff I think of when I am trapped in a sales meeting. A true BITOGers brain must have the answers to the questions regardless of the setting.

 

[Clevy]

Originally Posted By: ZeeOSix
Well obviously, as the oil viscosity goes up while keeping all other variables constant, the delta-p across the filter will increase. The largest difference in viscosity between two weights of oil would be with cold oil as apposed to hot oil.

The goal is to not create more delta-p across the media than what the bypass valve is set to crack open at. As you eluded to, there are many variables that create the delta-p. The combination of these variables will determine the delta-p seen across the filter at any given moment in time.

1) Oil viscosity
2) Oil flow rate through the filter from the pump
3) Filter media flow resistance
4) Total media area

Make the combination of these 4 variables result in the delta-p always below the bypass valve setting and you'll be "golden".

Great answer.
I've brainstormed about filters many times.
Ideally I'd want a filter that was "smart". And what I mean by that is wanting it to know when to open the by-pass,as well as being able to signal when its clogged.
I've gotten to know my car really well. The oil pressure at idle is consistent and I've found that based on the idle pressure I can tell when the filter is plugged and requires changing.
For example running 5w-20. When oil temp is 213f idle oil pressure is 19 pounds.
Now if the filter has trapped enough contamination oil pressure at idle will increase,it's just that simple.
So the key is to use the same products consistently so the numbers will be close.
So let's say I go with a thicker oil.
I'd have to establish hot oil pressure,with a new filter,then its as simple as observing the gauges and noting any anomalies.
I never had much use for real oil temp and pressure gauges. Dummy lights were good enough for me however now as I've gotten older I've come to realize that those 2 values are critical.
Otherwise I'd be just guessing if my filters done for and so on. Sure I can cut them open but you really have no idea if the filter was actually garbage,unless there is visible sludge and deposits caught in the pleats and such.
I've already learned how to read the gauges to determine how much oxidative thickening has/is occurred/occurring. The oil pressure increases and can then be compared to the virgin values noted when the oil was first changed.
It's like Caterham says. Using the engines oiling system as a viscometer.

 

[FutureDoc]

Originally Posted By: Barkleymut
Funny how that is the same kind of stuff I think of when I am trapped in a sales meeting. A true BITOGers brain must have the answers to the questions regardless of the setting.

Of course. The answer to every question is...




"It depends..."

 

[ZeeOSix]

Originally Posted By: Clevy

I've gotten to know my car really well. The oil pressure at idle is consistent and I've found that based on the idle pressure I can tell when the filter is plugged and requires changing.
For example running 5w-20. When oil temp is 213f idle oil pressure is 19 pounds.
Now if the filter has trapped enough contamination oil pressure at idle will increase,it's just that simple.

I've already learned how to read the gauges to determine how much oxidative thickening has/is occurred/occurring. The oil pressure increases and can then be compared to the virgin values noted when the oil was first changed.
It's like Caterham says. Using the engines oiling system as a viscometer.


If you are seeing an increase of oil pressure as the oil gets more miles on it, then it's probably due to the thickening of the oil as you mentioned above, not the oil filter getting clogged up.

I say that because with a positive displacement oil pump, and with the oil pressure sensor located after the oil filter (which is probably where the sensor is on you car), you can not detect if the oil filter is getting clogged up by looking at the idle oil pressure.

If you had a delta-p pressure gauge setup across the filter you could, or if you had the oil pressure sensor located before the oil filter you could. Another way is to know what the oil pressure is at a certain oil temp with xyz weight oil at near engine redline when you know the oil pump is at pressure relief (ie, when the oil pump is supplying a constant oil pressure supply to the filter/engine).

 

[dnewton3]

It's moot.

Any traditional filter (cellulose, glass enhanced, syn media used in the correct OEM spec'd application) will flow WAY more than the engine pump will deliver.

dP is important for that fractional second of start up when the valve may burp open to protect the media. I say "may" open, because it certainly doesn't happen all the time; Jim's testing proved this. The dP is importnat if you don't prefill a fitler at FCI for the same reason.

But operational use of a filter when the engine is running will almost NEVER see the bypass open, when means the media is flowing just fine. About the only time you're going to see the media be too restritive is when you neglect the fitler and oil to a point where the combination of plugged media AND heavily oxidized oil will combine to make the dP consistently high; how many BITOGers do we know that fall into this category? I ran a FL400S for 15k miles on W/M dino oil, and both the oil and filter were fine at the end of the OCI, with UOA and disection to prove it. In every day operation, the dP is practically NEVER usurped. Therefore the media is not the restriction point. Period.



Hopefully you're not going in the "tube" again, but if you are, ponder something else because this isn't worth the time.

You guys worry too much about things that simply never come to fruition. I realize that's the BITOG way, but how many times does this conversation need to take place?

 

[Clevy]

Originally Posted By: ZeeOSix
Originally Posted By: Clevy

I've gotten to know my car really well. The oil pressure at idle is consistent and I've found that based on the idle pressure I can tell when the filter is plugged and requires changing.
For example running 5w-20. When oil temp is 213f idle oil pressure is 19 pounds.
Now if the filter has trapped enough contamination oil pressure at idle will increase,it's just that simple.

I've already learned how to read the gauges to determine how much oxidative thickening has/is occurred/occurring. The oil pressure increases and can then be compared to the virgin values noted when the oil was first changed.
It's like Caterham says. Using the engines oiling system as a viscometer.


If you are seeing an increase of oil pressure as the oil gets more miles on it, then it's probably due to the thickening of the oil as you mentioned above, not the oil filter getting clogged up.

I say that because with a positive displacement oil pump, and with the oil pressure sensor located after the oil filter (which is probably where the sensor is on you car), you can not detect if the oil filter is getting clogged up by looking at the idle oil pressure.

If you had a delta-p pressure gauge setup across the filter you could, or if you had the oil pressure sensor located before the oil filter you could. Another way is to know what the oil pressure is at a certain oil temp with xyz weight oil at near engine redline when you know the oil pump is at pressure relief (ie, when the oil pump is supplying a constant oil pressure supply to the filter/engine).


Interesting. I wonder what kind of pain to expect plumbing in gauges like that

 

[ZeeOSix]

Originally Posted By: Clevy
Originally Posted By: ZeeOSix
Originally Posted By: Clevy

I've gotten to know my car really well. The oil pressure at idle is consistent and I've found that based on the idle pressure I can tell when the filter is plugged and requires changing.
For example running 5w-20. When oil temp is 213f idle oil pressure is 19 pounds.
Now if the filter has trapped enough contamination oil pressure at idle will increase,it's just that simple.

I've already learned how to read the gauges to determine how much oxidative thickening has/is occurred/occurring. The oil pressure increases and can then be compared to the virgin values noted when the oil was first changed.
It's like Caterham says. Using the engines oiling system as a viscometer.


If you are seeing an increase of oil pressure as the oil gets more miles on it, then it's probably due to the thickening of the oil as you mentioned above, not the oil filter getting clogged up.

I say that because with a positive displacement oil pump, and with the oil pressure sensor located after the oil filter (which is probably where the sensor is on you car), you can not detect if the oil filter is getting clogged up by looking at the idle oil pressure.

If you had a delta-p pressure gauge setup across the filter you could, or if you had the oil pressure sensor located before the oil filter you could. Another way is to know what the oil pressure is at a certain oil temp with xyz weight oil at near engine redline when you know the oil pump is at pressure relief (ie, when the oil pump is supplying a constant oil pressure supply to the filter/engine).


Interesting. I wonder what kind of pain to expect plumbing in gauges like that


Our member Jim Allen has a delta-p gauge setup on his "test truck". Maybe he can elaborate if he pops in here.

 

[ZeeOSix]

Originally Posted By: dnewton3
It's moot.

But operational use of a filter when the engine is running will almost NEVER see the bypass open, when means the media is flowing just fine. About the only time you're going to see the media be too restritive is when you neglect the fitler and oil to a point where the combination of plugged media AND heavily oxidized oil will combine to make the dP consistently high.


It's not 100% moot IMO. It all depends on how the 4 factors I listed above stack up. If for instance, if someone had a high volume oil pump and then used much thicker oil than specified for the engine it's possible the filter could see bypass events at very high engine RPM even with fully hot oil, whereas if a thinner oil was used, or an oil pump that wasn't insane with output volume it wouldn't go into bypass.

It's all a balance of the factors that effect the delta-p across the media along with the bypass valve setting used in that particular oil filter.


I do agree that filter loading with debris is one important factor to keep in mind also. If an oil filter became pretty restrictive over time from debris loading, then obviously bypass events are going to increase.