I have no facts as to the MB implementation of the odometer, but I'm a long-time computer guy who can make a pretty good guess. I'd say that they used non-volatile memory for the mileage and that you do not need to worry. This kind of chip retains the data stored in it even without power and they have been around for quite a few years. Keep driving and enjoyng that OM606!

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References