I've gone 240 miles before low fuel light several times. And sometimes it's slow cruising, and sometimes it's WOT. Weird. Normally it's 180 miles minimum on each tankful for me, which lets me skip every other fuel stop when we are all out riding. I was surprised that so many bikes have small tanks, or use fuel so fast, or both. But what you're trying is the best way to find out. Actually run it till it stops. But what I said, running it hard or in cold weather or something, might use it up slower or faster.