I was really hesitant on spending $40 for zMAX (www.zmax.com), especially when other fuel injection cleaners are less than $10.
But now I'm convinced that it works!
My 1992 Ford Ranger has an EPA rating of 18 MPG City and 23 MPG Highway. When I first got it just over a year ago, I averaged 19 MPG. When I first put in zMAX, I got 25 MPG, and now I get 22 to 23 MPG. Not bad for an old V6 truck.
I thought that was a fluke, so I tried it on a 1999 Honda Accord V6. It was averaging 18 MPG. But now it's getting 23 MPG after using zMAX.
Next, I plan on trying it on the Suburban which seems to be struggling with it's gas mileage.
Try it yourself and let me know if it works for you.