Re: 159 diesel drinks and drinks
My 2.4JTDM 159 has now done 34k miles and does around 40mpg at legal motorway speeds. It hasn't always achieved this - partly, I think, due to it improving with maturity and also other more mundane matters. I had problems with wheel alignment from new and these were finally sorted by finding a reliable tyre specialist (with optical equipment) plus a switch to Pirelli boots.
Raising the cruising speed to more normal M-way velocity has a marked effect and this suggests an aerodynamic penalty of some sort.
Booming around like a sportster also has a dramatic effect. It is, however, much more economical than my previous car (a much-loved 3.0 GTV) and I find it a good long distance vehicle.
Finally, you need to be warned of believing the mpg data from the cars own display. Both the fuel flow rate and distance measurements can be inaccurate for all sorts of reasons. Check them against other sources if you want to be certain.