If you want 50 to 1 ration, you need to figure out how many ounces are in each part. Divide 128 by 50 and you get 2.56. Therefore there … are a quantity of 50 2.56 ounces in each gallon. If you only need one quantity for the oil, then you need 2.56 ounces of oil.aking the world better, one answer at a time. if you are using gallon container (for example) a gallon is 128oz. divide the number of ounces of the container by the ratio which is 32:1. so divide 32 into 128oz. the answer is how much oil in ounces is needed for 32:1. that's the way for all ratios.