I have just purchased a "Ratio Rite" measuring cup to measure out my 2 cycle oil.
I would like to run Amsoil 100:1 at a 90:1 mix.
Here's my problem. The cup has lots of measurements.
Pints
CC
FL OZ
And a mix ratio for 1, 1.5, 2, and 2.5 gallons af gas. However, it only measures down to 70:1
What would be the best way to accurately measure a 90:1 mixture. The only mark on the cup lower than the 70/1 mark is 50cc. I'm not sure what my mix ratio would be at 50cc.

My only guess would be to put the cup on a digital postal scale and weigh it. Then fill the cup up to the 50/1 mark. Note the weight increase. Divide it in half to come up with a 100/1 mix. Then just add a teaspoon or so of oil to get close to 90/1.