by Dirtman » Fri Sep 17, 2010 2:00 pm
Most 2-cycle oil is marked in fluid ounces and gasoline is normally expressed in gallons. The units of measure need to be the same, so multiply gallons by 128 to convert to fluid ounces.
As 50:1, 32:1, 30:1 are all ratios of 1, we can drop the 1 in our calculations.
How we got here . . . calculating the amount of oil added to a gallon of gas for a 32:1 gas:oil ratio: 128 oz gas / 32 = 4.0 oz oil to be added.
We now have a 32:1 mix ratio and we want a 50:1 mix ratio. We know we already have 4 oz of oil added to the gallon of gas (128 oz), so changing the formula: 4.0 oz oil * 50 (we dropped the 1) = 200 oz of gas. 200 oz of gas is needed for a 50:1 mix ratio using 4 oz of oil.
Total of 200 oz gas needed - 128 oz gas we already have = 72 oz of gas that needs to be added to the 1 gallon of gas we already have mixed to convert a 32:1 mix to 50:1 mix. We now have 204 total ounces of mixture.
To double check: 200 oz gas / 50 = 4 oz of oil. The mixture is correct!