Hii there. I am working on the same projects. I have the same approximate 0,42V on Full Fuel and 3,28V on Empty Fuel. I use arduino Uno R3 with Voltmeter code, my only problem is that is very hard (for me :)) to transfor volts in litres especially because volt up is fuel down, and volt down is fuel up so i can`t use as volt/litres. A code or any formulas would be very useful. All the best and thank you in advance.