[QUOTE=Merica;3047010]I've also experienced a 2-3 mpg drop in fuel economy due to winter diesel.

However, there was a time a couple years ago when my 300D got around 22 mpg, maybe even a little less. Always baffled me, and since it was my first MB diesel I didn't have anything to compare it to. Then, in an effort to eliminate an oil leak by the turbo drain tube I removed and rebuilt the turbo. Immediately began to get 27mpg steadily. Also more power. Oil had been leaking past the seals in the turbo, turning into carbon and restricting its ability to spin. You can check for side to side play in the turbo shaft to determine if it's worn. I used a kit from **************.[/QUOTE

Checking actual boost pressure developed is something not discussed much if at all from a mpg perspective. Usually only suggested for poor performance if anything. A dragging turbo does make sense to me as a possible culprit.

Normally the turbo engines running well give better fuel milage than the natual aspired engines. So measuring boost prressure at operating levels under load should be part and parcel of lower milage claims than average.