[Nero_3D]

I expect that REFUEL_COST is for 100%, isnt it ?

Than its an easy cross-multiplication

Код:

100% fuel = REFULE_COST
fuelamount = calculation

pawn Код:

new calculation = (fuelamount * REFULE_COST) / 100;

Also I noticed that you create variables before you need it

pawn Код:

//
    new neededfuel = /* */; // not needed here
    if() { } else {
        if() {
            new calculation = /* */; // not needed here
            // neededfuel first time used
            if() { } else {
                // calculation first time used
                if() { } else {
                }
            }
        }
    }