Aviation Oil Filters Tested ~ 40% efficiency at 20 microns?

[2.7ecoboostFordBronco]

Vans Air Force Oil Filter Test

I didn’t find a thread discussing this here in a search, so feel free to link to it if I missed it. The testing was mostly geared toward assessing the effectiveness of the reusable challenger/k&p filters compared to disposable filters, in part due to champion/tempest shortages during 2020-2023.

I am posting it because I was curious about the thoughts of bitog’s oil filter experts on the seemingly low efficiency of the tempest and champion filters particularly. These are the mainstay filters of the piston powered airplane fleet. I was disappointed to see how low their efficiency is under 30 microns, but maybe that is an unfounded concern, or an imaginary problem on my part. They also cost about $50/ea.

On experimental, airplanes, the owner is free to choose any filter. On certified airplanes it seems to be a legal gray area. Some people on the linked thread were advocating to use the Wix filter instead of the aviation-marketed Champ or Tempest. Given the M&H QC issues I’ve seen discussed here I don’t know if I would risk that.

My questions are,

Is the lack of safety wire attachment points on the non-aviation filters a major concern given the relatively high vibration environment of an airplane? Maybe something like a K&N HP2004 with a nut that has a safety wire hole would be a good compromise for better efficiency? Then again, I’ve read of those nuts failing and causing oil starvation.

Lycoming and Continental, the airplane engine maker duopoly, specify 11-12 psi minimum bypass pressure, would auto filters bypass too soon? With that said apparently the champion aviation filters still bypass at 8-10, or at least they did the last I saw them tested in the mid 00’s.

How would the Lead in aviation 100LL load up a filter designed for car applications, like this Wix? As I understand it, dispersing/holding lead is a major function of piston airplane motor oil. I really don’t know how much of this an oil filter in an engine running leaded fuel cleans out. My oil analysis usually shows about 3000 ppm lead.

 

[ZeeOSix]

I didn’t find a thread discussing this here in a search, so feel free to link to it if I missed it. It is mostly geared toward assessing the effectiveness of the reusable challenger/k&p filters.

Based on the efficiency info in the posted table, I don't think I'd call them "filters". The other 3 aren't very efficient, Wix being the best of those three.

Are aircraft filters required to be safety wired?

 

[ZeeOSix]

On experimental, airplanes, the owner is free to choose any filter. On certified airplanes it seems to be a legal gray area. Some people on the linked thread were advocating to use the Wix filter instead of the aviation-marketed Champ or Tempest. Given the M&H QC issues I’ve seen discussed here I don’t know if I would risk that.

There are other filters on the market to choose from that will cross-reference to the Wix 51515.

 

[2.7ecoboostFordBronco]

Based on the efficiency info in the posted table, I don't think I'd call them "filters". The other 3 aren't very efficient, Wix being the best of those three.

Are aircraft filters required to be safety wired?

On an experimental there is no requirement. On a certified (Cessna, piper, etc) I think it’s another gray area. I’ve seen it discussed to use a hose clamp around an auto oil filter and safety wire to that.

 

[ZeeOSix]

On an experimental there is no requirement. On a certified (Cessna, piper, etc) I think it’s another gray area. I’ve seen it discussed to use a hose clamp around an auto oil filter and safety wire to that.

Yes, like below would work well. If I was flying or in an airplane, I'd definitely want the filter secured. Put the hose clamp close to the base where the can is stiffer.

 

[2.7ecoboostFordBronco]

Yes, like below would work well. If I was flying or in an airplane, I'd definitely want the filter secured. Put the hose clamp close to the base where the can is stiffer.

View attachment 268993

Thanks. I will probably keep using the Champion 48108-1 aviation oil filters for now while I look into this more. The 43% @ 20 micron rating just seemed really lousy for a $50 filter and I’m wondering if there’s something I’m missing. Then again many of these types of engines still use oil screens instead of filters, but with specified oil change intervals halved.

 

[Propflux01]

Thanks. I will probably keep using the Champion 48108-1 aviation oil filters for now while I look into this more. The 43% @ 20 micron rating just seemed really lousy for a $50 filter and I’m wondering if there’s something I’m missing. Then again many of these types of engines still use oil screens instead of filters, but with specified oil change intervals halved.

The engine will survive to its Time of Overhaul. (Think like old VW air-cooled, but with some filtration). Engine needs oil more than filter when at 7000 Feet. As for the $50, well, it shows a picture of an airplane on the box.

 

[dnewton3]

Wix reported at 7% at 5um and 78% at 20um is a far cry for their typical advertised "2/20=6/20" beta ... for whatever that's worth. Given that the filter test standard used is akin to the typical ISO protocol we're all familiar with, this begs the question of just how far off any one particular filter model (or even brand) these really are ?

 

[Cujet]

I suppose the one good thing about the Champion filter is quality construction. You know what you are getting. They are very unlikely to fail. I cut them apart at every oil change, always the same. Unfortunately, the price is now in the insane range.

I found this sloppy picture on the web, you can see the metal parts, bypass valve and spring, and rubber anti drainback valve.

 

[Cujet]

Items that stand out to me with regard to Aviation Oil Filters.

Typically conventional light piston aircraft use 50 viscosity oil, with some users choosing 15W-50 or 20W-50. Filter flow rate must be adequate to deal with this viscosity during run up, before oil is fully warm, without bypassing.

Lycoming/Cessna often allows an engine run up when oil temperature reaches 100ºF. But there are operators (flight schools with ops specs and so on) who require 120ºF oil temp before the throttle is pushed to the 1700/1800RPM point. My plane does not indicate if oil is over 100ºF, gauge is green band and a red line. Experience says the needle will be below the green band if it is less than 90º outside.

Also, the Champion filter has a nut for torquing it down, not just to remove it. The filter seal is failure/leak proof on Champion filters because of how it is captured, how much it compresses and the material chosen. It will work, hot or cold. The same cannot be said for non standard filters in aviation use. Aircraft use will find flaws that don't exist elsewhere.

The Challenger oil filter and it's aftermarket equivalent is a screen and while not a great filter, it is convenient and cheap. Unfortunately, too many have experienced in flight o-ring failure and leakage. I won't use one. Stainless filter elements can be epic good when designed and made properly, this one is not good enough on multiple fronts.

 

[wings&wheels]

I would guess that the low efficiency is intentional due to the suspended lead and amount of carbon and other contaminants carried by the oil vs. in a typical auto engine. This is one area that I would not choose to economize on via unapproved parts.

 

[2.7ecoboostFordBronco]

Items that stand out to me with regard to Aviation Oil Filters.

Typically conventional light piston aircraft use 50 viscosity oil, with some users choosing 15W-50 or 20W-50. Filter flow rate must be adequate to deal with this viscosity during run up, before oil is fully warm, without bypassing.

Lycoming/Cessna often allows an engine run up when oil temperature reaches 100ºF. But there are operators (flight schools with ops specs and so on) who require 120ºF oil temp before the throttle is pushed to the 1700/1800RPM point. My plane does not indicate if oil is over 100ºF, gauge is green band and a red line. Experience says the needle will be below the green band if it is less than 90º outside.

Also, the Champion filter has a nut for torquing it down, not just to remove it. The filter seal is failure/leak proof on Champion filters because of how it is captured, how much it compresses and the material chosen. It will work, hot or cold. The same cannot be said for non standard filters in aviation use. Aircraft use will find flaws that don't exist elsewhere.

The Challenger oil filter and it's aftermarket equivalent is a screen and while not a great filter, it is convenient and cheap. Unfortunately, too many have experienced in flight o-ring failure and leakage. I won't use one. Stainless filter elements can be epic good when designed and made properly, this one is not good enough on multiple fronts.

Thanks! Given all that, interesting that aviation consumer said the champion aviation filters still bypassed at 8-10 psi when tested. Another argument for preheat, I guess.

I’ve never seen a minimum oil temp for runup written anywhere for the airplanes I’ve flown, good to know that 100F is about what lyc/cont look for. I hate to say though, there are some days below 0F where it just isn’t going to get to 100 warming up at ~1100 rpm even if I sit there for an hour. My current lyc IO-360 powered plane’s AFM just says “The engine is warm enough when it idles at around 600 RPM and accelerates smoothly. Ensure the oil pressure is within the green arc on the gauge.”

 

[ZeeOSix]

Vans Air Force Oil Filter Test

View attachment 268987

I didn't go digging much into the chat board linked above, but wondering if they also did some ISO 4548 flow vs dP testing with "cold" (~500 cSt) and "hot" (~15 cSt) oil.

 

[2.7ecoboostFordBronco]

After I posted this, the test referenced in the original post became a published article:

Kitplanes Oil Filter Article

I am still using the Champion spin on filter but am toying with the idea of going to a carquest premium 85515HD which crosses to my applications and I would hope is a premium guard XL equivalent. Sure would be nice to go from 40 micron to 15 micron absolute efficiency, and save $200/year in the process. Interesting to note that the aviation filters are test to 500 psi burst pressure vs ~300 for car filters, and I do sometimes run 15W oil to the limits of the grade, as sadly, no one has developed an oil with a better winter grade for our engines.

 

[ZeeOSix]

After I posted this, the test referenced in the original post became a published article:

Kitplanes Oil Filter Article

Briefly scanned the article and it looks extensive. Will read it all later as it looks interesting.
https://www.kitplanes.com/oil-filter-testing/

I am still using the Champion spin on filter but am toying with the idea of going to a carquest premium 85515HD which crosses to my applications and I would hope is a premium guard XL equivalent. Sure would be nice to go from 40 micron to 15 micron absolute efficiency, and save $200/year in the process. Interesting to note that the aviation filters are test to 500 psi burst pressure vs ~300 for car filters, and I do sometimes run 15W oil to the limits of the grade, as sadly, no one has developed an oil with a better winter grade for our engines.

What's the oil pump suppose to limit the oil pressure to? What's the highest oil pressure you've seen? I'm assuming guys who fly don't rev the engine to take off power levels and take off before the oil temperature gets to some required oil temp? What's the max oil pressure seen when the oil is hot?

 

[2.7ecoboostFordBronco]

Briefly scanned the article and it looks extensive. Will read it all later as it looks interesting.
https://www.kitplanes.com/oil-filter-testing/

What's the oil pump suppose to limit the oil pressure to? What's the highest oil pressure you've seen? I'm assuming guys who fly don't rev the engine to take off power levels and take off before the oil temperature gets to some required oil temp? What's the max oil pressure seen when the oil is hot?

95 psi is what it’s set to for the limit. I’ve seen about that, for sure 90. 85 psi is the top of the normal operating range (oil warm). Usually it cruises at about 65 psi.

There is no warm up minimum temp before takeoff, just a 2-3 minute warm-up recommendation. The manual just states “the engine is warm enough for takeoff when it idles around 600 rpm and accelerates smoothly”.

I usually try to get the oil to 100F and CHT to 250F before takeoff but when it’s -20 it’s not always possible. I use a 15W-50 synthetic blend but the most common oil is an SAE50 monograde.

 

[Faawrenchbndr]

Thanks. I will probably keep using the Champion 48108-1 aviation oil filters for now while I look into this more. The 43% @ 20 micron rating just seemed really lousy for a $50 filter and I’m wondering if there’s something I’m missing. Then again many of these types of engines still use oil screens instead of filters, but with specified oil change intervals halved.

Nothing like an FAA certification turning a six dollar oil filter and do a $50 one

Yeah, that hose clamp thing works. I’ve done that quite a few times over the years.

 

[Faawrenchbndr]

Thanks. I will probably keep using the Champion 48108-1 aviation oil filters for now while I look into this more. The 43% @ 20 micron rating just seemed really lousy for a $50 filter and I’m wondering if there’s something I’m missing. Then again many of these types of engines still use oil screens instead of filters, but with specified oil change intervals halved.

Yeah, it is crazy. Almost seems like these filters are more of a strainer than my actual filter. However, when you’re in the air, dirty oil is better than none

 

[2.7ecoboostFordBronco]

Yeah, it is crazy. Almost seems like these filters are more of a strainer than my actual filter. However, when you’re in the air, dirty oil is better than none

This is true, and there might be some logic to sacrificing efficiency for capacity in this application so that the filter can “get you home” following a part failure without going into bypass. Going into bypass could cause damage from the unfiltered debris to completely stop the engine. Where I fly a complete engine failure in flight probably has a 50/50 chance of being fatal even if managed properly. This is certainly the argument Champion makes when you ask them why the efficiency is so low on their aviation filters.

At the same time the engine costs $80,000 new and an overhaul is at least $40,000 so minimizing normal wear would be nice. I think we could use a filter that doesn’t compromise efficiency quite this much and has sufficient capacity to limp the engine home in such a scenario. Luckily engine failures are extremely rare aside from fuel starvation due to operator error.

 

[ZeeOSix]

At the same time the engine costs $80,000 new and an overhaul is at least $40,000 so minimizing normal wear would be nice. I think we could use a filter that doesn’t compromise efficiency quite this much and has sufficient capacity to limp the engine home in such a scenario.

Does anyone make an add-on bypass filter for aviation use? That would be a way to ensure cleaner oil when a low efficiency spin-on is used. Of course with a bypass filter setup you have extra hoses and fittings that could be a risk point for failure too.