What is the best fuel mix for the most distance?

Mixing 60% gasoline  to 40% diesel will give you the max distance which is approximately 30 ish feet.

An easy way to get the fuel mix in the approximate ratios. Fill your 1 gallon fuel container half way with gasoline. When you have reached the half way mark on the container. Continue to fill another 2 inches above the halfway mark with gasoline. Then fill the remainder of the container with diesel fuel. That is the approximate mix of 60/40. 

You can experiment with heavier diesel mixtures but it becomes increasingly more difficult to ignite the stream.