There's quite a lot of material in old posts about this. General consensus was that engine and oil can run pretty hot. The water in my M113 (same as your M112 but with 2 more cylinders) runs between 90degC and 100degC most of the time and the oil is even hotter.

I'm glad you got your uneven running sorted, amazed about the fuel, will watch out myself in future.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190