Well, the 500:1 ratio is about the same that people seem to recommend. Four oz of Acetone to a full tank, or 15 gallons of gas, actually yields a 480:1 ratio, but that's close enough for me. This is my third tank in a row using it, and it seems to have inproved some, as I stated earlier. The only reason I ran multiple tanks is to remove the possibilty of inconsistent driving habits on my test. After this third tank, I'll go back to running without for a few tanks and let you all know what happens.