Thought I'd put a post up on how things went! It never started off as an experiment, it just moulded into one.
Basically 2-3 weeks ago I drove down to the Isle of Wight. For me it's a shade over 200 mile round trip. When I left home, I had 3/4 of a tank worth of fuel and the trip down was mainly motorway. I averaged about 85ish on the motorway. I was basically flowing with the traffic in the fast lane. I kept an eye out in front and tried not to use my brakes, judging traffic etc and when I accelerated back up to speed, it was a gentle acceleration. When I got back home, I had 1/4 of a tank left. Now that impressed me considering how fast I was going. Theoretical range of 400 miles per tank.
Today I've come down to Southampton for a couple of weeks and again, it was 100 mile drive down so I thought I'd go on a proper eco drive down to see how little fuel I could use. I basically treated the throttle like a bruised testicle and the speedo never saw anything above 70 mph on the downhill sections. I spend most of the time doing between 55 and 65 mph.
The verdict? I used 1/4 of a tank. The same as before when I was going a hell of a lot quicker!
The only thing I can put the result down to was because I was going slower, I had to use more throttle to get up the hilly bits, where as when I was cruising faster the momentum took me up it. Got to say though, plodding along was quite a nice drive down with the weather as it was!
On a separate note, I think I saw a member come past me on the M3. It was a black A3 (could have been an S3) and their number plate rang a bell. It was KEZ **** (followed by 4 numbers). I was the one driving miss daisy on the inside lane