Its 20 more miles too, but, i bet which ever car you are taking (assuming big Jag / Landy?) will be more fuel efficient at 80, than 50.
I doubt that's true for any car, TBH.
Kevin
I reckon my tractor was about double mpg doing 80 than doing 40. Related to the TC lockup I guess.
My 2.2 is more economical at shade under 80, than doing 50.
Sounds like 5th gear is a bit tall then. I think the opposite will be true in a diesel 4x4.
Kevin
In my 75 mile commute, i've experimented with cruise, and its defiantly no more efficient at 50. Tends to sit at 2k rpm then, slighest dip, hill becomes an issue, engine under load, sometimes needs a change down.
80, it feels just right, instant mpg readout is same as 80, and it just seams to float over all the little hills and bumpy sections. In the better weather got 34 mpg over the course of a tank with it set at 80 all the way.
3.0 diesel could well be different, but over the course of a run, i rekon there is very little in it, especially with a big heavy car