1977 300D oil pressure gauge

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Wayne Day - 04 Nov 2006 16:26 GMT

I know it's normal for my 1977 300D oil pressure gauge to be pegged at
45 during normal operation. However, at idle, sometimes it's just a
hair under the peg and other times it drops to 35 or 30 or so. Is this
a symptom of something I should be concerned about? Seems like it
should ALWAYS drop at idle.

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T.G. Lambach - 04 Nov 2006 19:39 GMT

Oil is thicker when cold than when hot so on cold start up the pressure
will be higher than later on after some driving. Hot idle pressure is
typically 50% of maximum, cold idle at or near maximum.

Another factor is the SAE weight oil in the motor - higher weights =
higher idling oil pressure.

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Wayne Day - 08 Nov 2006 14:10 GMT

In alt.auto.mercedes "T.G. Lambach" <tlambach@nohamorspamcomcast.net>
wrote:

>Oil is thicker when cold than when hot so on cold start up the pressure
>will be higher than later on after some driving. Hot idle pressure is
>typically 50% of maximum, cold idle at or near maximum.
>
>Another factor is the SAE weight oil in the motor - higher weights =
>higher idling oil pressure.

Yes, but sometimes it's ALWAYS up around 45- it doesn't matter if the
engine is hot or cold. It used to dip down to 30-ish at idle all the
time. Now, rarely.

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Richard Sexton - 06 Nov 2006 17:08 GMT

>I know it's normal for my 1977 300D oil pressure gauge to be pegged at
>45 during normal operation. However, at idle, sometimes it's just a
>hair under the peg and other times it drops to 35 or 30 or so. Is this
>a symptom of something I should be concerned about? Seems like it
>should ALWAYS drop at idle.

Nah, the number mean nothing. All that matters is it's pegged as soon
as you take off.

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