So after quite a bit of research on BITOG, Google, and several manufacturer websites, I can't seem to dig up enough data to answer my questions. I would like to know the efficiencies of common air filters. The only data I can find is from Purolator. The regular air filter is 96.5% efficient, and the oiled PureOne is 99.5%. They did not state what micron size. I am looking for data on WIX, Fram, Purolator, and AC Delco (unless I am forgetting a major one. This is for my Impala). I do NOT want ANY K&N filters or info on them. I know any big name SHOULD do just fine. However, considering Purolator is having oil filter issues, I have to question the air filters too, and therefore I am questioning every brand. The other question I have is (strictly comparing paper to paper) are there any flow differences between the brands, or any correlation between efficiency and flow? I am only considering standard paper and oiled paper filters. Thanks in advance!