Hi,
I'd like to share a graph to summarise my experiences with fuel economy for the X-type 2.2D and at the same time seek advice. At the moment, it seems that I am only able to post in the new member area, but I may repost in the near future to share my results with the community.

The graph monitors my fuel consumption (trip and calculated) and price per mile since the purchase of my Sovereign at the end of June 2011.

My typical driving make-up is very close to 50% motorway, 50% heary urban and this has been consistent for the 7 months.

The low fuel efficiency in the early days was because I was enjoying the novelty of having a new car and I was driving it really hard. 42 to 45 mpg is the efficiency I get for my natural driving style in the Summer.

A sharp derioration then unfolded in the late Autumn which was coincident with a severe EGR fault. The valve was stuck solid and rather than the regular stutter, sometimes my car struggled to start at all. The valve was replaced at the end of December and now performs normally but the fuel efficiency never recovered. The deterioration was accompanied with a notably larger deviation in the calculated and actual mpg.

I'm prepared to spend some money to fix this and share results with other users but I don't know where to start.
I'm looking to get it remapped, but feel this may be overlooking another problem so I may look at other things first.
Is there a connected EGR fault that could be having an effect?
Does my computer typically need resetting after an EGR replacement?
Is this typical Winter impact for a Diesal engine?
A local mechaninc suggested an oil change and new air filters without even checking if I needed one. Is this reasonable expenditure before a ECU reset or remap. Can it affect it?

I appreciate any advice, and will post the results of any repair.

 

I should also point out it is an 06 plate. The car is new to me.
Thanks again!