Yes, believe it or not - this is an old motorcycle driver (rider) trick. Be sure that you read the ingredients on the package to ensure that the moth balls are made of napthalene. A handful of these in a tank of gas will definitely make a difference. Depending on the compression ratio and original octane rating of the fuel you have available you will have to experiment some to determine the exact number to add per tank. As far as I know there is no down side and they are a lot cheaper than the octane boosters you find in auto parts stores.