W204 : MPG display inaccurate

[6cyl]

I have a 2010 C350 CDI. I average about between 40-42mpg on long runs according to the OBC (mpg displayed). brim to brim records shows that this is consistently 9% optimistic.

Is there a way of recalibrating the MPG calculation ?

 

[st13phil]

I had exactly the same problem with my 2011 E350CDI and asked the dealer if it could be recalibrated. They said they would, but it was never any different.