I've spent the last 5 years designing air induction systems for Ford and Chrysler. During that time I had to do a study on K&N filters because the OEM's were wondering how K&N could get such incredible results, of course they wanted the same results out of their OEM air induction systems. To make a long story short, K&N filters do not reduce the restriction in the air induction system and therefore show no improvement in horsepower. What K&N filters do is let in more fine dust particles and contaminate your MAFS with oil. The oil on the MAFS eventually builds up, causes the sensor to read low, thus leaning out the air to fuel mixture. In extreme cases (very rare) this can cause serious engine damage. Some of the "cold" air induction systems do provide lower restriction but it is often at the cost of sucking in hot underhood air or ingesting water into the intake. Neither of which is a good thing.

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1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?

Most of the dust an air filter is going to encounter is sand, grit, etc. which is silica. I installed a K&N filter with an oiled prefilter sock on my work truck recently. I have had 3 oil analyses done prior to establish a baseline. The analyses were all clean, engine in excellent health. Now I want to test after running the engine with the K&N to see if the silica and other particulates increase on the next oil analysis. It stands to reason and has been proven that an engine that ingests more dust will deposit more of the particulates in the oil due to blowby. So my informal test may or may not show an increase in silica and particulates. Time will tell. If the K&N tests clean I will continue to use it. FWIW I run and extemely "wet" K&N and prefilter sock to ensure the maximum tackiness to catch the dirt. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

Don't know about MBs, but the consensus on VW TDIs is that K&N filters are losers that spoil MAFs, that OEM paper filters work best.

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'91 300D 2.5 Turbo 330K
'00 VW TDI Golf, 190K
'67 BMW R50/2
'73 Norton Commando Interstate

Only time I've seen a K&N or any reuseable filter harm MAF electronics is when it's overoiled. Don't overoil, no harm is done. I've had an FIPK on a vehicle for over 70K miles and the MAF still reads it's G/sec just fine.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Yes there was a high coralation between MAF failure and the oiled air filters. I never have had a MAF failure on either of our TDI's and current one is only 3 years old with only 55k miles on the clock and running like a well oiled Singer Sewing Machine. But I haven't run a K&N air filter either.

Big thing on the TDI forum was a huge spike in silica in the oil samples of several guys running oil test on different brands, the only difference was the airfilter useage (K&N) and one K&N was installed after second oil sample testing and silica jumped so high the testing facility thought/stated they had unfiltered air coming in from airfilter failure or no airfilter installed as was stated earlier about the other high silica results.

The guys running the test with K&N filters liked to have freaked out, they check the seals on the airfilters, and even the intake tubing on the TDI's. It was finally decided by the guys running the oil testing on the TDI's that a big no, no, was the use of K&N filter's on the TDI diesel VW's. If I remember correctly there was one guy running a Amsoil airfilter and it was no where near like the K&N, but it was not as good as OEM accourding to oil sample testing.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.