When I had my first P38 (4.6 HSE) I would be driving round the M25 from around J12 Chertsey, all the way round to J2 A2 then into Stratford....then as the work moved further out it was A2 to Ebbsfleet, then M20 to Ashford (Kent).....No, if im doing a constant 70 on a clear run on motorway (usually sheffield - london) i average 20-21. If i'm booting it then around 17-18.
I would average 19-21 on those trips.....