13.1 liters / 100km.
The tank holds 70 liters. You can do the math on full tank cost (I don't know what the prices are where you are, since you didn't say). And "how much to fill up full" depends on how low the tank is when you decide to refill, doesn't it?
Compared to the Nissan Skyline? Don't know, sorry.
fueleconomy.gov