[oilburner]

Martin, to answer your original question, the 2.4D and D5 give the same economy because they are identical engines.

The only difference is the software, the 2.4D is a detuned D5. Mechanically, they are identical. Detuning will rarely, if ever, give improvements in fuel economy, it simply stops the engine from producing its full power output.

This is a common trick by manufacturers to sort out who really wants the extra power and is prepared to pay for it. They all do it.

A 2.4D with a tuning "chip" will give the same BHP as a D5 with the same "chip".

I wouldn't trust the 2.0D to be much better economy wise in the real world, it has been said that on a cruise the Volvo 2.5 five pot diesel is more economical than Ford's 2.0 four pot diesel. I haven't experienced the 2.0D myself, so can't say for sure.