kg and Litres in game

Driver Weight is measured in kg while fuel is measured in litres does the game use the ratio of 1 to 1 to simplify meaning a driver who is 51kg vs a driver who is 56kg will be as fast as having 5litres less fuel or is there more to it maybe a more complex ratio or no ratio at all?

Looked around and doesnt seem like anyone knows, with some guide straight up talking about fuel in kg anyway so no idea whats happening there. If it is 1 to 1 would seem extremely OP so curious.

When you put fuel on the car, you must not exceed the interval 45 to 50L, no matter how much the driver weights.

I don't think the maths in this game are that advanced, to the point where they use unit conversions (e.g from kg to L, although they do use lb to kg although idk if it's accurate) to decide the loss of time due to added mass. I think there is a unit being called "kg" which for example has the effect of 0.5 real life kg; if a real life kg has a one 1:1 ratio with liters, the in-game ratio is more like 1:2 real life liters... and then there is the other unit that is being called "liters" which is probably a random value used as a handicap to the car's pace that fits well with the games mechanics.

Interesting discussion that should be moved to the "Help & Support" forum.

Fun fact : in real life F1 the teams use the weight of the fuel to measure it instead of the volume. Simply because a liquid's volume depends on its temperature/heat while its mass/weight doesn't have this dependency on temperature and is more stable/standardized way to measure the amount of fuel.

I cannot be accurate so i will give an example.
Fuel has high value for speed as ballast (penalty if a player is above the level cap in rookie or pro tier).
lets say a kg / lit is around 0.050 to 0.100 sec per lap.
For driver weight now.
First of all we have have the car so lets say we have the same car for 2 drivers.
A driver has a value of speed for the car so lets say driver level 1 is 2 seconds slower per lap than a driver level 20.
in theory Weight of a driver have a value of speed for a driver also lets say 10% of speed.
10% of 2 seconds is 0.200 seconds also lets say that we have 100kg (maximum) and 51kg (perfect for male driver) 
so 100-51 = 49 kg so its around 0.004 seconds per lap more every extra kg of a driver.
all those numbers are in theory.