I do think these engines make more noise/vibration at low rpm compared to om 602 or 606. All of the 602's I have seen are like this and 606 are smoother. But the 606 gets 33mpg, and the 602 is capable of 47mpg (I was surprised, but managed this on a 200mile trip recently).

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1990 300d 2.5 turbo
1995 E300d