Going to the light doesn't necessarily mean much. I know the Retro has a bigger tank and you can ride further which is a plus also.
I have gone as far as 160 to the light coming on before and most the time it's 130ish. But at the light I never put much more than 3 1/2-4 gallons in. So no where near empty.
I average about 35-38 on my bike. It may be set a bit rich thru the programmer but runs good so I don't mess with it. I could probably tweak the programmer for a bit more mileage, but since I don't know what I'm doing, I leave well enough alone.
2002 VTX1800R Corbin Young Gun Seat, Programmer III usb, Saddlemen saddlebags, Stealth Fairing, shop built lowers and highway bars, desmoged and 1800 "C" risers.