Yes, bigger bikes don't seem to get any better fuel economy than small cars.
I have a Yamaha R-1, 1,000cc it gets about the same mileage as your VT did, maybe less, and when being run hard, ? low teens ? mpg.
Wow - I never would have thought an R1 would be that bad.
I get fairly steady between 41 and 46 mpg with my HD, 1868 cc - granted, it never sees the RPM an R1 will but still - volume wise...
