I dunno, I bought a bike, and while its definitely more fun than my 06 Mazda3 daily, they both get about the same gas mileage. And I flog both of them daily, and still average about 30mpg in the car and 32-33mpg on the bike, only difference is the bike takes premium. Again, not that much difference, but I can carry people/shit in the car and drive anytime, compared to the limits on the bike, but it sure is fun.
Just saying..I'm sure with other bikes this might be a different story,but my vtwin likes gas I guess.