OIL pressure weirdness??

1987 190E 2.3 78,000 miles. After driving on the highway for about 2 hours today noticed something weird when slowed down and was in normal traffic coming home after getting off highway. Oil pressure gauge at stops was dipping below the 2 mark. As soon as I pushed the accelerator it went back up to the top but at stops it would go back down. usually it stays up close to the top or at the top even when stopped. Is this normal or was it abnormal before and normal now? ugh, thanks

[G-Benz]

This is normal operation for MB vehicles.

Other makes calibrate their gauges to register nominally at all times...you may be used to those characteristics.

If you haven't already noticed, your coolant temp gauge will register all over the place...especially during the summer.

So don't fret unless your oil pressure drops to almost zero at any time, or your coolant temps get above 120 C.

Yes I have been noticing it on my coolant also especially today...It would go up quick then go down then go up high and come back down. I shouldn't worry?

[G-Benz]

Your cooling system has all sorts of backup measure to keep temps at normal levels...two aux fans as well as a clutch-driven main fan. Circuits that monitor ancillary systems and shut down if necessary (like the A/C compressor).

When you start up in the morning, your temps should read around 40C and begine to climb to around 85C - 89C. Usually this is where it will hover if your cooling system is working optimally.

On very hot days, it may climb a bit more, especially when sitting in traffic or at a light for a reasonable length of time. Then you might see temps climb to over 90C and higher.

But if temps seem to sustain 95-100C (or over) no matter the ambient conditions, then you may want to check out your cooling system efficiency.

I guess this post is getting away from the subject, but another question. how can I tell if my aux fans are working and properly? can I trigger them somehow? I have never heard or seen my aux fan go on?

[G-Benz]

They are mounted up front of the radiator. They come on when temps get hot. They are two speed, so they will run at low speed after a moderate drive and high speed if it's a very hot day, or the engine was under a heavy load for the trip.

You have a temperature sensor mounted either on your coolant pump or your cylinder head that when disconnected, the circuit operates in a "closed-loop" mode. The fans will run at high speed when you pop the connector off.