Been doing a lot of long distance riding and even with 5 gallon gas tank I have come close to running out of fuel several times. Range is very dependent on the riding style of the day, altitude, temperature, weather, and fuel usage ranges from 37 mpg up to 43/44 mpg. = range 185 to 220 miles. So I have purchased a 1 gallon spare fuel can for my ride, 93FLHTP.

Take a look at:

http://iwblogger.com/2010/reda-gas/

The quality of this product is excellent and the fit is outstanding. I have heard all of the downsides of carrying spare fuel but this product has addressed them all.