When looking for better fuel economy and performance gains a drop-in air filter for your car is a great way to see slight gains, while improving gas mileage. K&N is one of the leading makers of Performance Air Intakes and Drop-in Air Filters, They offer a million mile warrenty, which is much longer than any vehicle will ever drive for, so rest assured that you will always be covered no matter how old the vehicle.
Installing the air filter was extremely easy, all that was needed was unscrewing the air box where the stock air filter sits. Popping out the stock air filter and placing the new K&N filter, and reassembling.
If you are looking for true performance gains when dealing with your car's breather, I would not suggest a drop-in air filter, I would go with the more expensive complete air intake system. But if you are just looking for a cheap way to save gas in the long run, this is the perfect way to go, which is why I bought it.
Even though I knew not to expect much gains, after I installed it I took my 2003 Chev Cavalier for a spin and floor'd her. I was actually quite surprised with the power gained after the installation. Now most people buying this would like to know about the gas mileage, right now I am getting about 30-50 more kilometers per tank of gas than I use to.This is quite good for a ~$65 dollar investment.