My 2014 would get 42MPG at 80MPH very consistently, slowing down helped but not a huge amount. Gas light would go on at about 140 miles. The 2013 and newer have a trip computer which will show current and average gas mileage. On long trips on my current bike I have found the current consumption display to be my favorite. It may not be perfectly accurate but checking it a few times will give a good check. I like it as I know wether I'm doing better or worse for the current tankful. This becomes very important in places like Wyoming and Montana where gas stations may be a long ways apart. Variables that impact fuel consumption include speed, headwind, body position and luggage. In the US stuff like ethanol content will make a difference. Ethanol free will increase gas mileage a noticeable amount. Rain isn't good for mileage either although I generally go slower in the rain. In the last year I've done three long trips of 4,000 or more miles. It was surprising how much my consumption varied and sometimes I couldn't really figure what was the difference. My bike is a BMW F800GT and one of it's best features in the fuel efficiency. Ive not had a bike that could go as far at slower speeds. It has a 4 gallon tank and at interstate speeds has about the same consumption as my ZX6R 636 and CBR600RR did - 42 to 44 MPG. Slow down to 50 or 55 and it would get 65 to 70MPG! My ZX6R could never do that. It save me in Kansas on my first long trip, realized I wasn't finding gas stations so slowed down and stretched the gas. Made it to the first station 3 miles after the gas light went on.