I've tracked my scooter mileage in excel from day one. The other day I was noticing once again those little fuelly.com signature lines under some of you guys posts. I decided to signup and went back and plugged in all of my fillups. Feully.com shows me some stuff that just tracking by myself didn't allow (like seeing what other Super 150 owners are getting for mileage). Of course it relies on people being honest but so does most things in life. At every fillup I used to write the odometer reading on my gas receipt, then take it home and plug it into the excel file. This morning I used the iOS app that you can download and low and behold it pushed that data on the fillup right to my account and updated my stats.
If you religiously keep track of your scooter mileage then you should give fuelly.com a look if you don't use it already. It can also be used as a research tool when looking at new vehicles (look up real world mileage).
I figured out this morning that over the 2000 miles I've driven on my Super8, I've saved $132.00 in gas (~ $26 per month) versus driving my car that same amount. Fuelly.com helped me figure that out.