If you're brave, which I've tested and done hundreds of times, you could put plus and then add 3oz of 100% acetone to a full tank of gas. I've done it in my 2003 Accord and even felt a HP increase even with the car fully loaded!!!

The bottle of 16 oz only cost $3.00 or so from a beauty supply store. If you google acetone, you will find a bunch of websites that have proven this to work! In fact, I used it on my 1997 Civic DX and have gotten as high as 47 MPG!!! I have about 42 MPG with acetone. But you might be afraid to try it. No damage has been done at all over a year of doing this. It works and after speaking to an employee from Chrsyler, he told me that he have been doing this for a couple of years and has seen positive results!