Aside from the stop-start system, are there any other enhancements to the TD4-e that would improve fuel consumption? If I'm travelling at a steady 70 mph on the motorway in my non 'e' 2007 XS TD4, where clearly the stop-start system will have no impact, will my mpg by the same as a TD4-e, or are there other aspects of the newer car that would improve its mpg in this scenario?

I don't believe that there would be a difference in that situation. In addition to the Stop/Start function there is a 'gear-change light' to advise the driver as to the optimum time to change up to the next gear. Some people are able to choose the best time to change gear for the benefit of the engine, however for those who can't it means that the engine is balanced between not being over revved nor being laboured.

James

Other manufacturers change the gear ratio's on 3rd, 4th and 5th to drop the revs a bit and put low rolling resistance tyres on.