How would the consumption of a 2010 C350cdi compare to my 12 year old C220cdi? Much worse, slightly worse, roughly the same? I really need to get another Merc and I like these a lot. The last couple of times I checked my 220cdi over two tanks of fuel it came in at about 38mpg the first time and 42 the second time. Steady, mixed conditions. I would be very interested to know before I proceed any further.