NC Oil Pressure.

doc · Postby **doc** » Mon Apr 21, 2014 8:11 pm

O.K. Some of you may find this less than Smart.
But, My Car has strange oil pressure compared to every other car I have owned before.
When running down the road at or near the speed limit. The oil pressure is right in the center of the gauge.
However, it drops away a great deal at idle, And nearly peg's the gauge at high R.P.M.
In contrast, My Chevrolet and My Harley run constant oil Pressure at all R.P.M.'s.
The little Mazda runs like a champ, Makes little or no engine noise.
But , Still, Is this normal?

sailaholic · Postby **sailaholic** » Mon Apr 21, 2014 8:36 pm

If the others run constant oil pressure at all Rpm then the gauge is either a dummy gauge (think a low oil light that looks like a gauge) or they are generating enough oil pressure from idle that the pressure relief valve is always open generally indicating an overly thick oil.

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JBT · Postby **JBT** » Mon Apr 21, 2014 8:59 pm

It's normal for the NC. It is a faux gauge that is controlled by the ECU(?) to give a reading resembling something that a direct indicating gauge would show such as high pressure at medium to high revs, highish pressure at low revs when oil is cold, low pressure when oil is hot at low revs (especially idle) etc. It's entertaining to watch but as useless as the gauges on the post 1994 MX-5s which go to a fixed position regardless of revs and oil temperature.

A low pressure light would be useful. :roll:

Postby **orx626** » Mon Apr 21, 2014 9:04 pm

The NC has a dummy oil pressure gauge. I too was concerned when I saw the needle on L (Low) at idle.

I fitted an aftermarket gauge (Defi) to confirm this.

Cheers,
Danny

doc · Postby **doc** » Mon Apr 21, 2014 9:36 pm

Sailaholic. Me thinks you have never owned an American V-8.
The oil pump can spin 40 PSI at idle with 5W-30 at operating temps all day.
But good to know it's not a proper gauge on the Mazda.
As all my American Cars have always had a real gauge.

sailaholic · Postby **sailaholic** » Mon Apr 21, 2014 11:12 pm

They must be designed with a pressure constant oil pressure and a high volume relief valve. Not sure why, must be a reason though.

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doc · Postby **doc** » Tue Apr 22, 2014 8:05 am

Don't Know all the details on that Sailaholic. But I can say, over the years I've owned a number of American Cars.
They were all this way. Oil pressure might jump up to 60 PSI at startup, but quickly settle down to 40 as the engine warms.
I had a ford V-8 a few years back that when the oil was about due for a change, you could watch the oil pressure gauge "Bounce" at idle.
(Dropping off). Fresh oil fixed it straight up. I believe the engineers wanted plenty of pressure for the crank and rod bearings. As well as to keep those lifters quiet.
At any rate. The way my oil pressure gauge has acted in the little Mazda was new to me.
So I thought I'd ask. Glad to know it's normal for this car.