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Oil Pressure at start up.

shaunpr

Well-known member
Joined
15 Jun 2015
Messages
171
Just a quick question about oil pressure at start up with a cold engine.

Replaced my oil pressure sensor as it had gone faulty, it always showed 5 bar oil pressure at start up with a cold engine and the new one is doing the same.

Is this normal and then it drops off once warm?

Thanks
 
Yes that's normal. All my 911s have been off the gauge when cold. Drops to nearer a bar if idling and red hot. Should obviously rise and fall with revs when on the move and it will state in your owners handbook the minimum accepted pressure.
It used to be 3 bar at 5k revs but my cars have never been that low. Usually the other way round, 5bar at 3k revs.

It drops off when warm as the oil thins, hence less pressure.
There's a relief valve in there should pressure ever be too much so pretty safe really. It's when it's too low you want to worry. :wink:
 
I believe the 3 and 5 are a typo (ie they are meant to be the other way around)
 
Interesting. Would certainly make sense from my personal experience. :thumb:
 
Oil pressure is dependent on oil grade (XwY) and your engine wear/pump efficacy and the rpm.

The oil pressure gauge is as follows:

Cold start: any revs = 5 bar

Operating temp: idle = 2 bar (or less, dependent on exact model, engine wear, oil grade used - 1.5 bar or extreme 0.8 bar when very hot and racing).

The higher the better (within reason) - ie 2.2 would be fine

Operating temp: 3/3.5k+ rpm = 5 bar


Slightly warn engines will run slightly lower pressures for the same oil grade/temp.

If the normal op temp pressures are below 2 bar (not racing), you should consider a Xw50 or Xw60 next oil change.

Too low on cold start indicates (assuming pump OK etc), 5wY or 10wY at next oil fill,
 

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