Kevin, are you really sure you want to know?
Ok, my early calculations, which are not that accurate due to a lot of time spent on tickover at the SVA etc. and no long runs..........12 mpg.
I am assuming that on a decent run and with the engine getting a little more loose in time I'll be getting nearer 15 mpg. I'm off to France for a week in June, so I'll get more of a chance to work it out properly. Also, I have a diff change planned for the winter to swap the 3.31 for a 2.88 power lock.
Currently 85 mph in fifth gear is around 3000 rpm. Ok for acceleration, but as my lump pulls well from under 2000 rpm, I can up the gearing a notch.
Hope to be 2250-2500 rpm at 90 mph once it's all changed over. It should reduce the fuel consumption a bit and feel less "busy" on the motorway.
