PS fuel use is
massively different at 55mph to 70mph...
If you can cope with doing 55 on a motorway - around 1,400 revs ish - you
will get around mid 60mpg
Obviously this can only be done with a combination of looking about 2 miles ahead (and behind) for overtaking opportunities.
Its no good having to brake down to 50, then overtake at 60, and pretend that evens out at 55
