My 400E has always ran a pressure of 0.5 bar at idle, in gear, in summer, with AC on. The manual tells us clearly that anything above 0.3 bar is acceptable, as long as the pressure comes up immediately with increased RPMs.
Not to start YET ANOTHER thread about synthetic oil, but since the switch to Mobil 1 15W50, idle oil pressure is always above 1.0 bar even in summer. I just think it makes sense for this engine, which tends to run on the hot side, to give it as much protection as possible . . .