Review at 41,000 miles - average consumption, every litre logged in Excel spreadsheet (a bit sad, but informative), is 37 mpg - this has been stable since about 4,000 miles. Mileage is 90% open road and normally set cruise control at indicated 80 mph on dual carriageways.
I have attempted to model the effect of the DPF regenerations and estimate that the net affect is about 1 mpg - undoubtedly it would be worse if a lot of urban driving were involved. The reports of singificant improvements from DPF removal could well because because even when not regenerating, it creates excessive back-pressure?
There is no doubt that it does not help, but compared with previous diesel cars, which even if auto have all had better consumption, I would suggest that blunt aerodynamics and excessive weight are the real killers.