How to premix
If possible, it is is best to premix in a separate container -- as in, not in your gas tank. However, we don't all always have the foresight to fill up our gas tanks completely before leaving the vicinity of our separate gas containers, so mixing at the pump is a fairly common occurrence.
- Mixing in a separate container: Add a gallon of gas (or however many gallons your container holds) to the container. Add the appropriate amount of oil to the gas. Put a lid on the container, and shake it until the gas and oil are completely mixed.
- Mixing in the tank: If you do mix at the pump, be sure to turn your petcock off before adding oil or gas. This will prevent unmixed gas or oil from entering your fuel line and carburetor (both straight oil and straight gas can cause problems with your ped starting and running). After that, add gas to the tank until it is almost (but not completely) full. Check the pump to see how much fuel you added, then add the appropriate amount of oil. Shake your moped back and forth to mix the fuel and oil -- more shaking is better than less shaking. After you feel pretty secure that the fuel and oil are mixed, turn your petcock back on, and you should be good to go.
Note: when on the run 3oz of oil is a hair above the second line on an undented 12oz dasani water bottle. Which would be 40:1 with 1 gallon of gas,or very very very close. 50:1 is 2.56oz of oil to 1 gallon of gas, 40:1 is 3.2oz , and 32:1 is 4oz