DurAlt Fuel Conditioner improves the combustion efficiency of gas and diesel fuels, improving fuel economy by an average of 10% and lubricating engines for maximum performance! Because DurAlt is super-concentrated requiring only a tiny amount per tank, the savings on fuel alone pays for any size bottle and returns significant dollars to your budget. The larger bottle size you get, the greater the savings! Our 8oz bottle is perfect for treating normal size passenger vehicles and small trucks and can be kept in your vehicle door. Each 8oz bottle has a built-in measurement chamber making fuel treatment easy. The larger 16oz bottle is designed for larger vehicles, but is an economical option for refilling the 8oz bottle.