I just got finished installing my HKS circle earth kit (the purple one). I mounted the central point right on the negative battery and I have noticed that my car starts up much easier, idles smoother, and possibly revs smoother. The lights are brighter also.

I do not know about gas mileage yet, but I don't believe that anyway. And I didn't have a CD so I couldn't check the stereo.

I also modified the battery cover so it will fit with the circle earth in place. What I'm going to do tomorrow is cut a hole in the battery cover so the circle earth is visible. I also have two grounds left to cut and bolt, making a total of 7. I'll post pictures tomorrow.

Dan