After three tanks (2 oz in 15 gallons , 3 oz in 15 gallons, 1.5 oz in 15 gallons) I see no need to experiment any further.
Never saw anything more than 1 mile per gallon difference so far (Up and down), the same kind of mileage I always have seen with my PU.
I never noticed any difference in power or idle smoothness or any of that crap I read about. IMO it didn't do ANYTHING. PERIOD. there you go.....