Currently playing GW4, which is in the transitional period from piston powered aircraft to turbine powered ones, one thing occurred to me: the piston powered airplanes use quite a lot less fuel for a similar sized aircraft than the turbine powered ones do, even when corrected for speed. Now while I'm sure the AWS data on this matter is accurate a thought crossed my mind: they use different types of fuel! Piston powered airplanes use AVGAS, while turboprops and jets use JET-A. I honestly don't have the historical data on the price difference between the two, but at least today AVGAS is usually about 3 times the price of JET-A. If this correlation also existed in the past, than the game would unfairly favor piston powered airplanes compared to real life.
I think the most elegant solution to this would be to have two graphs on the fuel chart, one for AVGAS, one for JET-A. On the aircraft page it would be specified which kind of fuel is used by this airplane. Something like "1890kg/h AVGAS" for a DC-6B for example. I would imagine that the two graphs start rather close together and start to drift apart over time, making piston powered airplanes more expensive to run as time goes on. But I think this should be loosely based on historic data, so someone would need to check that out.
Hope anyone besides me finds this idea interesting.
Cheers,
Cedric