Remember, Mustangman, Byron calculates their percentages by weight, not Volume like other manufacturers such as Morgan, Wildcat, Redmax, etc. Byron's 15% nitro, 20 % oil by weight fuel equates to about 11.4% nitro and 17 to 18% oil by volume. Byron's 10% nitro, 16% oil fuel has about 7.4% nitro and 13.5 % oil by volume.