Ya know, I'd like to just mention this experience of mine without babbling too long so here goes. Several years ago I bought a Purolator Air Filter for my '04 Altima 2.5S. Just the regular Puro, nothing special! It was on sale so I picked up one. Looks well made! I still have the OE filter that the Altima came with along with a FRAM Air Hog. Don't ya know that every single time I install this PURO filter I get the worst MPG tank after tank winter/summer it doesn't matter. I'll run this Puro for a month or so at a time and when I change back to the(a bit dirty) factory OE filter, my MPG jumps back up to the mid 20's. I currently have the Puro in the car now! Yes the temps are cold but I'm going to change back to the factory and again see it my MPG jumps back up. I'll bet it does, even if just a little. The Puro looks brand new/clean and the factory OE that came in the car looks dirty but when held up to the light, well, you can see the light! I'll finish this tankfull of gas, read the MPG and change to the factory filter again. The factory OE filter is free of debirs, just dirty looking with wavey pleats and the Purolator is perfect. Mentioning that I also have a FRAM Air Hog, I use this only in summers and I don't really notice anything on either side of the spectrum but I bought it for 7 bucks/new(last one at PB's) and IMHO, the orange filter FRAM Air Hog has a K&N look to it. I don't know how much the factory Nissan air filter cost but I'll guess it's in the teens or maybe $20 bucks. It doesn't look like anything special. It's made OK but, there is something about it that allows better MPG or maybe airflow. The Nissan paper element is actually kinda thick/restrictive looking. It has more pleats than the PURO. Any comments? I'm just babbling!