Solved

How does fuel affect cars weight???

I have played this game for 7 months and I don't understand how 1 or 2 litres of fuel more affect the cars' weight.Like the lap times between a car with 14 litres of fuel to a car with 15 litres of fuel around Monaco

Interesting...

Only why anyone can test that out is by having identical twins racing for them.

You cant run one season and then the next with a higher or lower fuel. Track temp, driver or car ratings might be different the next season.