What a can of worms! No mention of jet sizes, riding style, "two up" or on your own, luggage, average speed, commuting/highway use, weather conditions, etc. I recently rode one of my bikes (BMWK1100LT) on a 1500 mile ride, so for planning purposes, I did a "shakedown" ride of 500 miles earlier in the week. On that ride, I consistently averaged 60 MPG. (Imperial gallons, not those teensey weensey US gallons) With those numbers, I calculated that I could easily do 180 miles per tankfull, with another 25% in reserve.
You can imagine my surprise when the engine conked out on the first leg after just 200 miles? Oh dear. While I washing pushing this enormous blue lump the last 3 uphill miles back to the gas station, I realized that whereas beforehand I'd been cruising at around 70 MPH with next to no luggage, on this trip I was burning up the road at an average of 90 MPH, with 30-40 pounds of luggage. After I rolled out of the gas station, I recalculated my fuel stops at the 120 mile mark, and had a great ride after that.
The best way to calculate your economy is just to fill it right up, ride it for 50 miles or so, fill it up again, and do a "miles per gallon" calculation, not forgetting all of the variables, like I did. Cheers, Terry.
