K&N air filters are a gimmick! The oil can get on your Mass Air Flow sensor and thus reduce your gas mileage!
Get either Wix or OEM from dealer, count the number of pleats to compare Wix (from O'Reilly Auto Parts) to the OEM. If you don't know if you're installing it backwards or not, turn on just the electric of your car and run the air on low, stick a piece of paper in there without letting go and you'll know/feel/see which direction is the air flow. Also. Take a picture of each step as you take it apart and note the position of the old one.
If you are gonna stick with K&N save your old filter so you can have a filter in there while your K&N is taking hours to dry in the sun from being re-oiled. Use the squeeze bottle and not the spray so you don't over-lube.
What i wanna know and need help with is determining WHEN to change your engine air filter. What does Scion recommend? Mechanics say to flip it over, look at the backside, and hold it up to the sun or shine a light through it, if the light is too blocked-opaque then it's time to change. Having a clean engine air filter is important to ensure optimum gas mileage. For the cabin it's important if you want your car to smell good and filter odors (if you get an odor-absorbing/activated-charcoal one from either Autozone STP-brand or NAPA Auto Parts. I usually get the NAPA one because it's less expensive and in-stock. It's usually dark in color and usually higher price than regular but not always.
