How much oil is added to 20 liters of gas at 50-1 ratio?

To calculate the amount of oil needed for a 50:1 ratio, you can divide the total volume of gas by 50. For 20 liters of gas, you would add 20 liters ÷ 50 = 0.4 liters of oil. Therefore, you should add 0.4 liters of oil to 20 liters of gas at a 50:1 ratio.