The last time I changed the oil in my 03 Ford Ranger and 03 Subaru Forrester I had Blackstone do a UOA on the oil from each. The Ranger oil was Mobil 1 and I ran it 8,022 mi. The Forrester oil was Mobil 1 EP and I ran it 10,973 mi. The Ranger had about 22,000 mi. on it and the Forrester had about 45,000 mi. on it. I ran a new Pure One oil filter in the Forrester and a new NAPA Gold oil filter in the Ranger. Both vehicles had a new K&N air filter in them. For the Ranger oil the silicon was 20 ppm and the universal average was 15 ppm. The comments from Blackstone said that the ppm for aluminum, chromium, iron, copper, and lead were "far too high". They ranged from 2 to 8 times higher than the universal averages. For the Forrester oil the silicon was 21 ppm and the universal average was 11 ppm. Aluminum, chromium, and iron ppm were 3, 2 and 5.5 times the universal averages. The comments from Blackstone said that "High silicon may be dirt getting past the air filter". Now I can't conclusively blame the high silicon content of the oil and the high engine metals wear on the K&N's, but they are an obvious culprit. It was enough for me to throw away the K&N's and switch back to paper filters. And by the way, neither vehicle showed increased mpg or hp from using the K&N's.