240 divided by approx. 11 gallons (12.2 gallons being a full tank, but you don't use all 12.2 gallons) equals around 21-22 miles to the gallon...

i run 310 on a full tank and i have a gsr as well, and occassionally i punch it here and there... and thats when the gas light barely comes on.. so around 28 miles to the gallon..

240 isn't rilly normal