Check Kyote's post and think about this. You get better mileage at higher elevations. I've been in a good position to observe this, because I'm at sea level in Corpus Christi, and have made many trips to the west coast. (In a cage, sadly, not on the FJR.) If you check your mileage carefully, you'll find you can tell the difference with a little elevation. If it's so in the car, it should be so on the motorcycle, maybe moreso, because the drag coefficient of the bike is probably a lot higher than my sleek Lincoln sedan.