Fuel economy

[Troon]

^ This.

I believe most fuel is burnt by continual unnecessary acceleration and deceleration / braking. Look ahead and plan how to make the most of the momentum you've built up.

On the flip side, it doesn't use any more fuel to accelerate to a given speed with "enthusiasm" than doing it gently. If you're joining a motorway and will be cruising at speed for a significant time, giving it the beans (but no more than about 80% as many engines overfuel at very high loads) on the slip road is no less economical than getting up to speed like Hoke. Don't use this strategy between roundabouts or traffic lights though...

 

[Klausy]

Well I did suggest that this would get the grey matter warmed up.

The results and therefore a conclusive answer to my initial question, after a couple of weeks driving the same journey is as follows:

Sticking to 55mph - Averaging 44mpg
Sticking to 60mph - Averaging 41/42mpg
Sticking to 70mph - Averaging 38mpg

So, its a compromise between the time you have for the journey, the money you wish to spend on fuel and how bl**dy bored you get whilst sat on the M6/M69 doing 55mph..

Thank you all for your thoughts and comments, some of the maths has been quite spectacular.