Do you? 3 ounces of Lucas Octane Booster treats 5 gallons and will raise octane by 30 points. This means if you add 3 ounces to 5 gallons of 91 octane, you'll have 5 gallons and 3 ounces of 94 octane fuel. Since this bottle is 15 ounces of additive it will treat 25 gallons of fuel if you dump the whole thing in.