To get a good mileage you need to record the amount of petrol you put in the tank and mileage and ideally put it into a spreadsheet so it can calculate the last average mpg and the total mpg. Now you have a base for checking data.
My runs are at consistent speeds on dual carriageways and do 30 miles with only one roundabout so there is hardly any accelerating or braking. Any vehicle is economical doing this as long as you do not go fast (over 60mph) as the aerodynamics rob the efficiency. (drag is proportional to the speed squared).
I have logged the fuel consumption for 25000 miles and always have achieved over 80mpg commuting. Before I used it for commuting I still got over 60mpg. I enclose a graph from the spreadsheet.
http://forums.sv650.org/attachment.p...7&d=1291575586
Graman