Scooter fuel economy

My fuel gauge is coy. It's a five LED display that prefers to give gentle hints about how much petrol I have left rather than just come right out with it. So I noticed last time I filled up that my mileage was exactly 17000 kms. I thought, "Aha! I will remember that, and use it to calculate my miles per gallon or whatever the youngsters are calling it these days". So I rode for a while until the gauge intoned to me that just maybe it was that time again. When I pulled in to Shell on the way to work my mileage was exactly 17200 kms. "How about that" I thought. "This will make my sums a little easier". The tank seemed pretty dry. I filled it right up so the fuel was a couple of millimetres from spilling out. It was exactly 7.00 litres. I was a little startled by this. I thought perhaps God doesn't trust me with decimal arithmetic. So anyway, I crunched the numbers in Excel, double checked with Matlab, and I can now reveal the following analysis:

Distance: 200km
Fuel:     7 litres
Economy:  3.5 L/100km

I also discovered my round trip to work is 13 km, so that means I should fill up every 15 work days, with a 5km margin for error, (unless I take trips to the shops or the video store). Now that's some applied mathematics. A Honda Jazz is supposed to get 5.7 L/100km. A Prius is supposed to 4.4 L/100km so my scooter beats them by not by that much considering it's a scooter.