Grand Prix 500
Main Motorcycle: 2013 Tiger 800XC
Join Date: Jan 2006
Location: Norman, OK
Other Motorcycle: 1967 TR6C
Extra Motorcycle: 1989 Honda NT650
He certainly did know, and followed manufacturer's instructions for each of the makes and types they evaluated. They had a vested interest in keeping their equipment running, and costs minimized. They were not trying to sabotage one product against another. The conclusion they came to was that the K&N let more dirt in than the good paper filters, to the point where the life of the engine was affected.
Our street bikes generally don't have the conditions or duty cycle of open pit mining equipment, so we can install a K&N and not see a difference before we trade off. But I won't choose a couple of max-rpm horsepower over dirtier oil. I tend to keep my gear a long time - I sold my Ford Econoline [into commercial service!] after I had driven it 320,000 miles, and it never needed to have the engine opened up, never burned oil. My present car has over 100,000 miles, and I have two vehicles over 50 years old [both have had rebuilds].