I got an email from someone asking about 2 stroke oil/fuel ratio for an older Vespa Piaggio Ciao moped . The moped comes with a measuring cup near the gas cap for measuring the correct amount of 2 stroke oil to add to the fuel. On the measuring cup it says 2%. The question was "how much oil do I add to the fuel and what does 2% mean?" Normally the oil/fuel ratio is specified using ratio's like 40 to 1 (40:1) or 50 to 1 (50:1). Instead of using a ratio, Piaggio decided to use a percent to specify the oil to fuel ratio. If you have a mixture of fuel and oil, and you want 2% of the amount of fuel to be two stroke oil, than you want to mix the fuel and oil at a ratio of 50:1.
1 gallon of fuel = 128 ounces of fuel
128 ounces of fuel / 50 = 2.56
2.56/128 = .02, .02 x 100 = 2%
128/2.56 = 50
Therefore, mix 1 gallon of fuel to 2.56 ounces of 2 stroke oil to get a mixture so that the two stroke oil is 2% of the total amount of fuel, or a mixture of fuel and oil that has a 50:1 ratio (50 parts fuel to 1 part two stroke oil).
Your probably better off never using the 2% cup Piaggio included with the moped and mixing all your fuel and oil in a gas can before pouring the mixture into the moped. This way your measurements are more precise and your able to ensure the oil and fuel have completely mixed together by shaking the gas can before pouring the mixture into the moped.