Fuel/weight/weather/time settings have been kind of janky as long as I remember.
It may have got better at some point but after SU5 it has definitely been pretty hit and miss whether you enter the actual sim with the same time/weather/fuel settings you applied in the World Map.
Even within the world map it resets for me, if you set the fuel and then revisit it after doing something else (checking the map or checking call sign for example) the fuel is back at its defaults within seconds of opening that menu item.