Hi Steve,

One problem in dealing with volume is that so many different units are used to measure it. Cubic yards, cubic feet, gallons, quarts, pints, cups, fluid ounces, tablespoons, teaspoons and on and on. You didn't say what units you are going to use to measure the oil. I am going to assume fluid ounces.

I need to know how many fluid ounces are in a pint. The World Wide Web gives us a very useful way to find this conversion. Just type How many fluid ounces are in a pint? into Google or any of the major search engines. You can also ask google or Siri this question. When I did so I got 1 pint is 16.65 fluid ounces.

You now want to fill a 16.65 fluid ounce container with 51 parts, 1 part oil and 50 parts gasoline. 16.65 divided by 51 is 0.33 which is very close to $\large \frac{1}{3}.$ Thus put $\large \frac{1}{3}$ of an ounce of oil into the 1 pint container and then fill it with gasoline.

I hope this helps,
Harley