Just back from a ski run to the French alps in my new (to me) 2004 LC5 auto with 87,000 miles. Used 3 tankfuls but only 2 where I had totally steady speed on the autoroutes, the middle tank included lots of cold (-10 degrees) starts and trips up and down the hill.
On the way down I was being a bit pushy - had the cruise control locked on 84mph, which incidentally resulted in exactly 80mph (only had one toll booth during that tank, so I think this probably means around 81mph whilst actually cruising). I got 22.8mpg. On the return journey we had an easy target Eurotunnel so set the cruise at 78mph, which resulted in 75mph actual on the road (again, one toll booth) and I got 25.6mpg. In both cases, brim-to-brim top-ups and dead-steady speeds - gotta love payage autoroutes at night! At the time I was a little disappointed with these figures as I had hoped for a bit more - I get around 21-22mpg out of my 80 VX on longer journeys in Zambia at around 70-75mph and thought the LC5 with the D-4D would be a bigger improvement. It seems not!
Load: 4 adults plus ski kit, but no roof-box or skis up there. I did also raise the tyre pressures to 32psi.
Hope folks find this a useful first post!
Marcus