Hiya
Il2 uses SI(metric) measurements, so Kg for weight of fuel
in/out temps are the temps of the 'in' line to the oil radiator and the 'out' line of the same (or the game calculated values of these
)
the 273 part indicates the minimum of 0 deg Kelvin (absolute zero=-273 deg approximately) - it's output is in deg C
IL2 game engine seems to use oil out for overheat purposes, and would be the one to use for your instruments