To make a 50:1 ratio mixture of gasoline and motor oil, add 30.72 ounces of motor oil to 12 gallons of gasoline. This concentration is often used in small power tools, such as weed wackers and snowblowers.
In order to calculate the amount of motor oil to add to the gasoline, it is helpful to know that 1 gallon of any liquid contains 128 fluid ounces. 12 gallons therefore contains 1,536 fluid ounces. A 50:1 ratio is found by dividing 1,536 by 50. The result is 30.72 ounces, or rounded up to the nearest integer, 31 fluid ounces of motor oil.