The EGR has nothing to do with the oil pressure. A healthy MB will peg the guage when cold at start-up, but if it does this before the engine is running, as was posted before check the sender AND your ground connection. I have seen some really weird guage stuff when a ground was not properly connected that defied all logic.

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1981 300D 147k
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1979 300D 234k (sold)
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