If a fuel additive in the amount of 8oz per 128 gallons was enough to show remarkable engine improvement, the epa would have mandated it long ago as all of the ingredients are available at the refinery.
Adding 10-15% Ethanol decreases the mileage yield of gasoline, and yet here we are. I've never felt the EPA had my health, household budget, or the environment in mind while making their proclamations. While snake oil has been around a long time in various forms, I believe some products do work as claimed.
