I want to change my original vote dagnabbit!
With a T cam the highest ever was 33 mpg. (sitting on the motorway)
With an A cam the highest ever was 32 mpg. (sitting on the motorway)
Now with a stump pulling M cam I've just hit a new PB of 36 mpg, rather easily it seems as that wasn't all motorway. Oh, and that's with a clapped out air filter, dizzy cap, and HT leads.
Curiously, with this cam the fuel cut off seems to happen at 1600 rpm (that's right around 32 mph indicated in 4th gear). Although I think the cut off is related to road speed, and maybe the reason I didn't notice this before is because the engine sounded like it laboured a bit in 4th at that speed.
The most fuel efficient speed for my car on the motorway appears to be 67 mph indicated.