This is a rather odd question, but IMO, has some merit... My friend is runing an unscientific oil filter study. He using a constant oil (Pennzoil 20w-50) and a constant milage (2750) and a constant driving pattern (normal driving with a few rallycrosses thrown in for good measure). Car is a 1985 Nissan 300zx non turbo in good mechanical condition and has had regular changes in it's life. The so far the results seemed odd. with the known poorer filters less oil has come out of the car and with the known good filters more oil has come out. He has saved all the oil and measured it and each time when he refilled the car he put in the same amount of oil and it was filled to the same level. No top off was added in the testing. The filters have not been cut open yet either. K&N- 4.3 quarts removed. cleanest looking and not gritty PureOne- 4.1 quarts removed. near K&N and not gritty. Pennzoil (Fram)- 2.1 quarts removed. Oil very dirty looking These were the only ones he told me specifically about. He also told me that Napa gold produced similar results as the FRAM. This one was tested immediately after the k&n was. My question is, what would cause for there to be less oil with the "crappier" filters. I'm guessing it would be since the oil was more contaminated it burned off. Is this correct or is this logic as flawed as the experiment?