Kevin
Guys/Girls. It'e really not diifficult. If you've done a couple of races with the same fuel and engine supplier there's no excuse for fueling incorrectly. It's simply a case of working out the litres/km from the previous races...
Fuel consumption per lap is different at every circuit. The length of the circuit is not listed here and I suspect not simulated to the exact, real length. Only the fuel usage per KM can be looked up - for a circuit you have already been to. Next season, it will be easy. This season, accurate fueling is impossible. Or you are a much better strategist than I.