I ride a lot with 2 RSTD's, one guy gets 45mpg and the other riding 2up gets 42mpg consistently. I have a RSV and 2up I get 42mpg as long as its under 75mph. We all run pretty close mgs's if we are riding solo. Same tire pressures, same suspension pressure, the only difference being body weight and wind resistance with the RSV faring. So I loose..... 1/10 of a gallon per fill up at 150 miles but I have a radio. So do I really loose??? Plus I have an extra gallon of go juice so maybe I win.
I check mileage at every fill up. And yes I do the math so this analysis is based on 3 bikes at at least 20,000 miles all on the same roads, at the same speed, with the same wind, hills, speed limit ect.....