Oil gauge
 

I have a 88 420 SEL. the oil gauge goes to 3 when car is running. is that normal or should it go up and down as the engine speed increases and decreases?

3 when you're driving. Hopefully no lower than 1 when idiling.

Sixto
91 300SE
87 300SDL
83 300SD

oil gauge
 

It stays on 3 all the time. except when engine is off.

If it's not on 3 when you turn the key to on before starting the engine then you're in good shape. If it goes to 3 before the engine's turning, something's not right.

It's not uncommon to see MB engines idle at 3 at operating temperature but it's more common (I think) to see it dip a little.

Sixto
91 300SE
87 300SDL
83 300SD

funny,but just recently my guage started going to about 1 unless i was using the throttle and then it would close to 3.as far as i can recall it was always at 3 while running but just the other day -after idling for about an hour:eek: -i got back in and noticed it was idling around 1 and only at 3 while under power.could i have done something wrong by idling or is my oil sender just about to give it up?:confused:

I use the oil pressure gauge as something of a FSS on the 300SE. When the oil pressure gets close to 1 at hot idle, it's time for me to change the oil.

Sixto
91 300SE
87 300SDL
83 300SD

Sounds about right...
 

My car idles around 2.5 after being warmed up.

Goes to 3 with throttle.

Before I did an oil change (10,000km) 2 months ago, the idle was at 2 so i guess you can treat the oil pressure gauge as a FSS.

But never seen my oil pressure go any less than 2.

Maybe it's different for different cars???

Who knows...

When started cold, it idles at 3.

My $0.02...

If it goes to three when you just turn the key to the "on" position, then you have a bad oil pressure sender...