[FS~Daedalus]

Hello whiskey-charlie,
I am not member of the Team Daidalos but I think I can at least answer your first question.

I assume that we talk about aviation gasoline (AvGas 80, 82UL, 91, 100LL, 100), and this fuel has, depending on what kind of fuel it actually is, a density between 0.73Kg/L and 0.78Kg/L at 15°C (lets use the average of 0.755Kg/L).

physics teaches us:
density = mass/volume (ρ = m/V)
-> V = m/ρ


With a given fuel-load of, lets say 100Kg of aviation gasoline, we now have:

volume V = Mass m / density ρ
volume V = 100Kg / 0.755KG/L ≈ 132.45 Liter

There are two different gallons in use, the Imperial Gallon (4.54609 Liter) and the US Liquid Gallon (3.785411784 Liter). I assume IL-2 uses the US liquid gallon, Team Daidalos, can you confirm that?
OK, 100Kg of AvGas have a volume of 132.45 Liter, and that is (assuming it is US liquid gallons):

1 US Liquid Gallon = 3.785411784 Liter
-> 1 Liter = 1 / 3.785411784 US liq. gallons
-> 132.45 Liter = 132.45 / 3.785411784 ≈ 34.99 US liq. gallons

--------------------------------------------------------------------------

I can only guess what the answer to your second question might be...
I think the oil-in and oil-out temperatures refer to the oil-temperature before the oil enters the oil-cooling device and its temperature when it leaves the cooling-device OR its temperature before it enters and after it leaves the engine. Only these two cases make any sense to me... so you could test it:
Is oil-in temperature higher than oil-out temperature? -> temp. before and after cooling device.
Is oil-in temperature lower than oil-out temperature? -> temp. before and after engine.

Hope I could help a bit,
Daedalus