A few days ago I drove my recently purchased (from Canada) '05 cdi from DC to Florida in one day to get it titled. Took just under 16 hours door to door and was doing 68 mph most of the way. Average economy was 52 mpg with the best per tankful at 57 mpg and thats with the windows down.
I'm in the process of removing all those decals from the courier company I bought it from. Half done and its a PITA especially in the heat and humidity down here