Firstly, last checked, these V11s should only be getting 91+.
Times when I know I'm blowing through a full tank, I'll run fuel system cleaner to clean the throttle bodies. I know not to let that stuff sit in the tank or it'll eat the tank up.
But running 91 with clean injectors, if ran like a rational human being, though a tuned ECU, I can squeeze 38-42mpg. The fuel light will pop on at around 175-190mi but will still a bit. But riding like I stole it? 32..
If you're on top of maintenence, clean injectors, fuel filter, oil, etc, these are pretty good economically. Despite being a big girl.