I commute daily on the bike and normally, when dry don't worry too much about MPG, I overtake on the single carriageway A2 and "keep up with traffic" on the dual carriageway A2 (80ish).
I fill up just after the light comes on and stick in £20/£21 woth of fuel on todays pricing.
For the last tank I made sure all aceleration was gentle, stuck to all speed limits, didn't overtake and did 60 mph on the dual carriageway, WOW, I couldn't believe the difference it made.
The petrol light normally comes on about 175 miles, but by driving like I've stated above it came on at 207 miles!
So I saved an extra day's commute in petrol, but boy was it boring, especially on the dual carriageway.
The upshot is, I'm going to try and do 2 commutes a week being good and 3 like "normal". Easy while it's raining, that slow you down a bit anyway, but I doubt I'll be able to resist once the weather warms up and the roads are dry