[QUOTE=Amsoil Dealer Group;105175]No personal opinion here. I own a filter test machine and spent a lot of Money testing other filters and the K&N. Donaldson has had tests performed and show how poor of a job the K&N does in filtering. Some of RACOR's filters are made by K&N and say right on the box "For Marine Use Only". When I went to school at RACOR, I asked a question (I already knew the answer) "Why for Marine use only?" Right in front of everyone he said " We don't have to worry about dirt over the water, just need to keep the chunks from getting in the engine".
As part of a "Performance Upgrade" on my bike, a K&N filter was installed. My oil analysis came back "High Silica (Dirt) and Elevated Wear Metals (over 560 ppm)" Analysis report recommended checking/replacing filter. Removed the K&N, installed an AMSOIL Filter which, flows as well as a K&N and filters up to 50 times better. Although I ran about 600 miles on the K&N before my filter came in, the next oil analysis showed only 50 some PPM of Wear Metals and the oil was still good at over 10,000 miles.
K&N even says that their filters do better as they get dirtier... No Brainer but, I want to catch as much dirt as possible before the filter "Starts to work".
They are a performance filter designed to flow air, they also flow dirt.
I don't know if I should or shouldn't qualify myself here? I got alot of experience repairing stuff. In this newer age it seems its all about "Certifications" when I started it was about "fix it right or I'll beat your ass when I catch you". That said, as Fleet Maintainance for LaFarge International we were warned to weed out any K&N filters in trucks we overtook in any merging of small cement companies for maintainance through our department. The above quote is almost word for word that our oil change interval review/test center informed us off.