My E320 developed a noticable vibration at idle (500 rpm). It is not as though the engine developed a miss, it's more like an out of balance vibration. It goes away at higher rpms.

It smooths out a little when I shift into neutral (700 rpm), but it also smooths out in Drive at 700 rpm.

I opened the hood and watched the engine as I shift from Drive to Reverse. There is no big jump of the engine.

Could it be worn engine mounts?

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95 E320 Cabriolet, 169K