Using your cup measurement to make your 4.75 gallons of the following fuel.
20% nitro
20% total oil
60% alcohol
You will need
8 cups nitro
8 cups total oil
24 cups alcohol.
1. Assuming that the 'cup' being used has a volume of 8 fluid oz, the above recipe is correct, but it will make 2.5 gallons, not 4.75 gallons. (4 cups = one quart. 4 quarts = one gallon.)
2. Since there are 4 cups in a quart, the recipe simplifies to 2 qts nitro, 2 qts oil, and 6 qts meth. To make 5 gallons, put in 1 gallon of nitro, one gallon oil, and 3 gallons of methanol.
3. What all this boils down to is that for 20% nitro, 20% oil fuel, just put in 1 part nitro, 1 part oil, and 3 parts methanol. The 'parts' can be cups, liters, mouthfulls (wouldn't recommend that), gallons, buckets, barrels, whatever.