I put this in my 1999 Nissan Altima and noticed a change in the "get up and go" right after I put it in. Hasn't improved my gas mileage at all, actually I have been getting about 1-2mpg less, but my driving habits have been sporatic since I have put it in so it is hard to get a good calculation; it didn't improve though. For the money, convenience, and "health" it brings to my car, this air filter is more than worth it, it's an investment.