in the duromax test the ac delco wins all the tests , their filter is a throwaway at $40 and designed to last 1 year, the KnN is $60 and reusable but in that 1 year period does need to be serviced a number of times - like 4 times is my guess ...
they threw alot of dirt at these filters, over 1lbs of dust each - thats alot ... the ac delco did remarkably well holding it but suffered in air flow allowing on average only 33% of the K&N throughput , but I know for sure the K&N would need tobe serviced to hold that much dirt ... on a single oiling it held just under 1/2lbs
at the end though efficiency across 9 filters only varies 3%, and the K&N flowed 3 times better that the ac delco which they chart but again praise the ac delco cause its holding 1lb of dirt - milage gotta suck at that point ... I agree more flow means more particles just like bigger tires means more drivetrain stress , the air makes a few extra horsepower and I enjoy it, I have put 50,000 miles on my K&N and the intake tube is very clean - the only residue if from the crank vent in my case ...
I am not saying K&N is the best in all/any applications, but its a reasonably well performing filter if maintained and in the long run can be cost effective ... the purpose of this post is for those running open air filters including other brands but specifically K&N that you can extend your service interval by putting a cover over it that restricts little airflow and repels mud chunks and splashes from prematuring ending its service interval ...