Oil Filter Study - Mileage vs Clogging

[twX]

I found an interesting study that measured the mass of contaminants in oil filters vs mileage for almost 1000 oil filters used in real-world conditions. The used oil filters were mostly from small-displacement gasoline and diesel engines from car dealers and taxi fleets in countries around the world.

The most interesting finding of the study was that 90% of vehicles could travel 30,000 km on an oil filter before it became clogged, if the filter had a dirt holding capacity of 13.4 g. 50% of vehicles could travel 82,000 km before the filter became clogged. The least contaminated filters in the study only picked up 1 gram of contaminants per 60,000 km, so clogging would be expected after these filters were in use for 800,000 km (assuming operating conditions could remain unchanged over this interval).

There was no significant difference between clogging rate between turbo and non-turbo engines, or gasoline and diesel engines. Oil filters from countries with higher ambient dust conditions (Africa, Australia, Middle East, South America) had around 50-100% higher rates of clogging compared to the filters used in Western Europe.

The study is SAE 2012-01-1754: Oil Filter Clogging Rule - Correlation between Mileage and Lab Test Clogging. I don't think the forum rules allow me to post a link to the full study, but if you were to somehow find some sort of online HUB for SCIence papers, you could probably probably post the study title in the search engine and it would pop right up.

 

[MSCH]

I agree... 13 grams is about 1/2 an ounce.. how long does it take to have 1/2 ounce of particles in oil and how many milligrams of contaminants are in engine oil in the real world..?

its also worth saying air filtration is more important than oil filtration when it comes to removing wear contaminants before they get a chance to do any harm. oil filter is after the fact

 

[fantastic]

Interesting stuff. I wonder if they ran any extended oil filters in this test, standard, or a mix.

 

[CharlieJ]

Probably why some manufacturers say to only replace the oil filter every other oil change. It's not going to get clogged in 5K miles...

 

[twX]

Interesting stuff. I wonder if they ran any extended oil filters in this test, standard, or a mix.

Probably a mix, with mostly standard filters. They only measured the rates of contamination in grams per 1,000 km, then calculated the km-to-clogged figures based on a standard filter with a 13.4 g dirt holding capacity, which is probably a bit more capacity than the average oil filter from the small car engines in the study (1.2 to 3.0 L). Larger engines with smaller filters would clog more quickly.

 

[ZeeOSix]

I don't think the forum rules allow me to post a link to the full study

Why not ... it's just a link to something on the internet. People here do it all the time when referencing SAE studies, etc.

 

[ZeeOSix]

If you look at the majority of the engines in the study (the two highest peaks in the data), they put 1 gram of contaminates in the filter about every 5000 km (3,107 miles). So if the filter could hold 13 grams holding capacity before it was considered time to change it, then it would be 13 x 5,000 km = 65,000 km (40,359 miles).

Not sure what most "average"/OEM/jobber filters have for holding capacity before the dP gets too high, but 13 grams is up there somewhat. I think the old PureOne advertised their filter to hold around 13 grams. IIRC, Motorking said that Fram considered the worse case of 1 gram per 1,000 miles and uses that to rate the "up to mileage" rating on the filters. Obviously, if a filter maker puts a mileage rating on their filters there's going to be a lot of headroom in the rating.

 

[ZeeOSix]

its also worth saying air filtration is more important than oil filtration when it comes to removing wear contaminants before they get a chance to do any harm. oil filter is after the fact

Yes, but once contaminates get into the oil, the oil filter is the only thing left to remove it, besides an oil change. And contaminates get into the oil from other sources beside the air coming into the engine.

 

[CR94]

... IIRC, Motorking said that Fram considered the worse case of 1 gram per 1,000 miles and uses that to rate the "up to mileage" rating on the filters. Obviously, if a filter maker puts a mileage rating on their filters there's going to be a lot of headroom in the rating.

Similarly, vehicle manufacturers also have to allow for worst-case conditions when they decide on recommended oil filter change intervals. Therefore, under reasonably favorable conditions, a clean-running healthy engine can safely go much farther, as this study illustrates.

 

[twX]

Why not ... it's just a link to something on the internet. People here do it all the time when referencing SAE studies, etc.

Link to the study

 

[MSCH]

Yes, but once contaminates get into the oil, the oil filter is the only thing left to remove it, besides an oil change. And contaminates get into the oil from other sources beside the air coming into the engine.

true dat, but the amount is miniscule compared to what the air filter removes and what draining and refilling the crankcase on a regular basis accomplishes. engine oil generally accumulate wear and combustion by products, but that abrasive stuff coming in thru the air intake will ruin an engine faster than not changing the oil..

 

[twX]

true dat, but the amount is miniscule compared to what the air filter removes and what draining and refilling the crankcase on a regular basis accomplishes. engine oil generally accumulate wear and combustion by products, but that abrasive stuff coming in thru the air intake will ruin an engine faster than not changing the oil..

This is corroborated by studies that show that engine wear increases more or less linearly with dust ingestion, so an engine will have 100 times the wear if run without an air filter, vs one that is 99% efficient. Engines run without oil filters only experience around 3 times the wear vs engines using standard efficiency filter. So, if an engine occasionally runs with a clogged oil filter, it shouldn't cause a lot of excess wear.

 

[MSCH]

This is corroborated by studies that show that engine wear increases more or less linearly with dust ingestion, so an engine will have 100 times the wear if run without an air filter, vs one that is 99% efficient. Engines run without oil filters only experience around 3 times the wear vs engines using standard efficiency filter. So, if an engine occasionally runs with a clogged oil filter, it shouldn't cause a lot of excess wear.

exactly... abrasive particles venturing into the combustion chamber get trapped between the rings and cylinder wall... effectively become lapping compound that isn't going anywhere whereas any particulates circulating thru the lube system after filtration tend to be smaller than the minimum clearances in the lube system and tend to flow thru where they stand a good chance of getting trapped in the oil filter.. figure average bearing clearance might be .003" in, whereas a 30 micron particle is about .001" and things smaller than 30 microns just flow thru under pressure..

 

[Alien]

If you look at the majority of the engines in the study (the two highest peaks in the data), they put 1 gram of contaminates in the filter about every 5000 km (3,107 miles). So if the filter could hold 13 grams holding capacity before it was considered time to change it, then it would be 13 x 5,000 km = 65,000 km (40,359 miles).

Not sure what most "average"/OEM/jobber filters have for holding capacity before the dP gets too high, but 13 grams is up there somewhat. I think the old PureOne advertised their filter to hold around 13 grams. IIRC, Motorking said that Fram considered the worse case of 1 gram per 1,000 miles and uses that to rate the "up to mileage" rating on the filters. Obviously, if a filter maker puts a mileage rating on their filters there's going to be a lot of headroom in the rating.

According to the Ascent testing results, the Purolator Boss had a 12.5 gram capacity, the Wix XP 18.1g, the Delco Ultraguard Gold 9.1g, the OG Fram Ultra 13.6g, and the Royal Purple 10.1g.

 

[CR94]

... figure average bearing clearance might be .003" in, ...

Really? Considerably less on the loaded side, I believe. That's MOFT.

 

[ZeeOSix]

Really? Considerably less on the loaded side, I believe. That's MOFT.

Yes, way less than the bearing clearance spec. MOFT is typically around 25-30 microns (~0.001 inch) for a bearing with 0.003 inch clearance. Under high engine loads (max piston combustion force), the MOFT could get down to 5-10 microns. If the bearing could perfectly center while running, the MOFT would be half the total clearance.

 

[twX]

the MOFT could get down to 5-10 microns

I've seen measurements even much lower than this in normal engine operation, sometimes < 1 micron. This is from the 1992 NYC taxi cab study:

I've read elsewhere that the most damaging particle size in engines is around 4-6 micron, with very little wear from particles <2 micron. I suspect that 4-6 micron particles are the worst for wear since they are more numerous than larger particles, larger than typical MOFT, and usually remain relatively unfiltered by the oil filter. Even air filters have poor efficiency in this particle size range until the filter gets loaded up with enough dust.