I had the same problem with the oil light, bought a “T” fitting for the oil switch and the tubing for the mechanical gauge with a 1 inch diameter dial and it’s hiding at the side of the steering column and also keep the idiot light, the reading is still at 3 bars on the mechanical gauge.
Hope this helps.

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2000 430 ML
2005 S500
87 300 D
61 300 restoring