Actually this (and the following fuel calculator) is wrong because the proportions of the fuel part (the methanol and nitro) doesn't change when adding oil. In the OP's fuel there are 10 parts nitro and 78 parts methanol and this is what the engine runs on (and gets tuned for). No matter how much oil is added there'll still always be that same 10 parts to 78 of the actual fuel to run the engine with. To make it easier to understand, if you use a fuel with only methanol and oil then the engine runs only on the methanol (100% of it). Add some oil and the engine still only runs on the methanol even though you'll have had to open the needle slightly to account for the extra oil but the fuel side of it is still just 100% methanol.