I wish I could test my bike in a relatively stable area without all the variables I seem to encounter. My run to Seattle goes over 7 mountain passes or hills over 2500 feet in vertical climb. I live in an area where the wind blows almost constantly (today at 0600 it was blowing at 25 mph steady and gusting to 35 mph). I went for a ride on Saturday of 130 miles one-way. Going down (with the wind) the gauge showed more than 1/4 tank left upon arrival (no light on arrival, but it came on when I went to leave). Coming back into a steady 35 mph headwind, I was almost empty upon arrival - same route, same distance, mostly same speed, same number of stops.
My speeds vary depending on safety factors like wind direction (a 40 mph crosswind gets treated a lot differently than a 40 mph headwind or tailwind), traffic (how many times do I pass the trucks and motorhomes on the two-lane road), and route (unfamiliar backroads verses pounding the slab). Then you can throw in the differences in regional (or national) differences in fuel. Eurogas vs. Canadian vs. U.S. 10% ethanol crap, vs. Oz or Kiwi. Then there are differences in manufacturers of fuel and additives or seasonal differences in the U.S. for the EPA's Clean Air fetishs.
The only thing that makes sense to me is to accurately calibrate fuel in the tank with the gauge (like Mike5100). It seems to me that we can only get meaningful numbers for fuel mileage when we compare one rider to one bike. Just a hundred pounds between riders can mean significant differences in fuel consumption. As much as I'd like to, I'll never get close to MsLizz's numbers as I probably outweigh her by about 200 pounds without the 20 pounds of goatskin I pack on my butt. And one of my boots probably outweighs both of hers (and to put you at ease, MsLizz, I don't weigh 450 pounds).
