The Difficulty with Oil Analysis Reports

[Jackson_Slugger]

Yes, Doug Hillary wrote an excellent article on the utility of Used Oil Analysis that is featured on the main page of the site:
https://bobistheoilguy.com/used-oil-analysis/

Is he still around here?

 

[Spector]

I used to do the labs every oil change years ago, lab results are really trend analysis and as noted, if you change anything in the mix it can affect the results. Overall, other than coolant in the oil etc, I concluded the results are pretty much useless (maybe in deciding which oil to use but that would take many samples) So, I stopped doing them, even if lead (which I did have) was high or another wear metal so what, not really a lot one can do about it and changing the oil more often does not solve any issue. I decided not to waste my time or money doing them.

 

[OVERKILL]

Is he still around here?

Yes, though hasn't posted much lately. I've spoken with him off BITOG and he's a very busy man.

 

[Tom NJ]

Used oil analysis tells you more about what the engine is doing to the oil than what the oil is doing to the engine.

Therefore not a reliable way to compare oils.

 

[HowAboutThis]

I used to do the labs every oil change years ago, lab results are really trend analysis and as noted, if you change anything in the mix it can affect the results. Overall, other than coolant in the oil etc, I concluded the results are pretty much useless (maybe in deciding which oil to use but that would take many samples) So, I stopped doing them, even if lead (which I did have) was high or another wear metal so what, not really a lot one can do about it and changing the oil more often does not solve any issue. I decided not to waste my time or money doing them.

I've never done one, but think they're interesting to read through at times. Waste of money for most people following an interval in their owner's manual or maintenance minder that drive reasonably normally (nothing extreme). Like, I do 7000-8000 on a non-DI Toyota that says 5k severe, 10k normal. It ends up being about 6-8 months. A UOA would probably say, given my commute, "10k-12k". But I need the tires rotated anyway at that mileage, so what's 20 extra minutes on a day I have time to change myself or bring it somewhere? I more or less change based on "when is it close to time, and when do I have time to do it."

 

[ZeeOSix]

Changing air filters too often would in most instances be counter productive as far as engine wear goes. We've been told time and again that filters become more efficient as contaminates accumulate in the filter media, (up until a certain point of course). In fact just opening up the airbox unnecessarily to check or replace can let unwanted contaminates enter. OEM air filters should in most cases be good for 30k miles, maybe more. Another case of more is not necessarily better, or let sleeping dogs lie.

Air filters get more efficient as they load up with debris ... but oil filters don't. Oil filters typically become less efficient as they load up due to the increased delta-p built up from loading causing the already captured debris in the media to slough off and do downstream.

 

[AEHaas]

I have seen the compelling evidence that air filters work better after they are loaded up some. Yet my own serial oil testing has shown significant decreases in dirt in the oil after an air filter change. And there is always a decrease in wear metals to go along with it. 'Not sure what is going on but that is my experience. As such I change the air filter more often.

Ali

 

[madeej11]

I have seen the compelling evidence that air filters work better after they are loaded up some. Yet my own serial oil testing has shown significant decreases in dirt in the oil after an air filter change. And there is always a decrease in wear metals to go along with it. 'Not sure what is going on but that is my experience. As such I change the air filter more often.

Ali

If the air filter is more efficient then how is your oil cleaner after an air filter change. Seems if it's less efficient when new then the oil would be dirtier, not the opposite.

 

[4WD]

Used oil analysis tells you more about what the engine is doing to the oil than what the oil is doing to the engine.

Therefore not a reliable way to compare oils.

Indeed - on an expensive industrial engine - a good UOA is a verification - not a ticket to run outside of OEM recommended hours …

 

[Owen Lucas]

Air filters get more efficient as they load up with debris ... but oil filters don't. Oil filters typically become less efficient as they load up due to the increased delta-p built up from loading causing the already captured debris in the media to slough off and do downstream.

How does an air filter become more efficient the dirtier it gets? I would assume that if there is more debris blocking the media then air flow would be reduced?

 

[ZeeOSix]

How does an air filter become more efficient the dirtier it gets? I would assume that if there is more debris blocking the media then air flow would be reduced?

Filtering efficiency and air flow isn't the same thing. I'm not talking about the "efficiency" of the flow volume, but the efficiency of the filter to remove debris from the air flow volume. Air filters have a very small delta-p across them, whereas oil filters have a relatively pretty large delta-p across them.

Air filters do flow a little less as they load up and become more restrictive - but the delta-p increases in only a few inches of H20 ... not multiple PSI like on an oil filter, so the delta-p stays very low and the already captured debris pretty much stays in the media - unlike oil filters. The debris accumulation causes the flow paths to become smaller and therefore the air filter becomes more efficient without delta-p increasing enough to caused debris sloughing.

I'm sure if an air filter became almost completely clogged, then captured debris would start sloughing off and it was then become less efficient. I've seen air filters basically caved in because they became so clogged.

 

[Owen Lucas]

Filtering efficiency and air flow isn't the same thing. I'm not talking about the "efficiency" of the flow volume, but the efficiency of the filter to remove debris from the air flow volume. Air filters have a very small delta-p across them, whereas oil filters have a relatively pretty large delta-p across them.

Air filters do flow a little less as they load up and become more restrictive - but the delta-p increases in only a few inches of H20 ... not multiple PSI like on an oil filter, so the delta-p stays very low and the already captured debris pretty much stays in the media - unlike oil filters. The debris accumulation causes the flow paths to become smaller and therefore the air filter becomes more efficient without delta-p increasing enough to caused debris sloughing.

I'm sure if an air filter became almost completely clogged, then captured debris would start sloughing off and it was then become less efficient. I've seen air filters basically caved in because they became so clogged.

Thank you for clarifying, makes sense now.

 

[Quantico]

I have changed air filters every few years.. never really tracked miles or how dirty they are. If they look kind of dirty...not filthy or terrible its time to just swap them out. I have three air filters i am ready to swap in my three vehicles. And will buy a few more in a year or two. I live in a city and dont drive dusty dirty roads or where farming is going on.

 

[mooseandsquirrel]

If the air filter is more efficient then how is your oil cleaner after an air filter change. Seems if it's less efficient when new then the oil would be dirtier, not the opposite.

I do not ascribe to the fact that a slightly dirty filter is more efficient. Perhaps with an oiled gauze filter but not with a paper filter. Paper filters are hepa filters like are used in aerospace clean rooms. They filter very well. Of course when full, they restrict airflow which is why they need to be replaced periodically.

 

[Bill_W]

Blackstone maybe not good for TBN but that number from other labs are useful for figuring oil change. Oil formulas change and is nice to see on a UOA that you are getting what you paid for. But molecules are compounds and atomic elements measured in PPM are misleading to the quality of the oil. But it’s fun to do. A shame that the oil tests that qualify for API certification is not made public. You have to rely on Project Farm to show you wear scars and frozen oil races.

 

[madeej11]

I do not ascribe to the fact that a slightly dirty filter is more efficient. Perhaps with an oiled gauze filter but not with a paper filter. Paper filters are hepa filters like are used in aerospace clean rooms. They filter very well. Of course when full, they restrict airflow which is why they need to be replaced periodically.

I'm thinking Hepa filter efficiency may be a little too restrictive as an engine air filter.

 

[Krieg]

Used oil analysis tells you more about what the engine is doing to the oil than what the oil is doing to the engine.

Therefore not a reliable way to compare oils.

Profound statement. I like it!

 

[ZeeOSix]

I'm thinking Hepa filter efficiency may be a little too restrictive as an engine air filter.

Yeah, HEPA filters are way more efficient than even the highest efficiency passenger car air filters. HEPA filters typically have mega filter media area in order to flow enough air.

 

[madeej11]

Yeah, HEPA filters are way more efficient than even the highest efficiency passenger car air filters. HEPA filters typically have mega filter media area in order to flow enough air.

Are Hepa filters also unsuitable for cabin air filters?

 

[ZeeOSix]

Are Hepa filters also unsuitable for cabin air filters?

After doing some searching, it looks like Bosch makes a HEPA cabin filter, which they claim meets the efficiency definition of a HEPA filter. The air flow rate going through a cabin filter isn't anything near what flow goes through an engine air filter, so apparently a HEPA filter can be used for cabin filters.

https://www.amazon.com/Bosch-6055C-HEPA-Cabin-Filter/dp/B01JYSX028

https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter-1
"HEPA is a type of pleated mechanical air filter. It is an acronym for "high efficiency particulate air [filter]" (as officially defined by the U.S. Dept. of Energy). This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm)."