1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

What is your oil pressure at idle???

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Old Feb 7, 2004 | 02:31 PM
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What is your oil pressure at idle???

Just want to judge if mine is doing ok. I took her out of the garage today and warmed her up. After warm up she idled very nicely, but the pressure seemed to level at around 60. What is yours??

John
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Old Feb 7, 2004 | 02:41 PM
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thats where mine sits at. I'm pretty sure its not the most accurate gauge in the world but thats where it hovers around when everything is working so I just watch to make sure that its always around the 60 area.
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Old Feb 7, 2004 | 03:26 PM
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the oil shouldnt be at 60 on idle, it should be more around the 30 mark. 60 when you are crusing about 70-80 when accelerating.
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Old Feb 7, 2004 | 03:53 PM
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60 psi at Idle is pretty high.... but not dangerously high.... most likely just a guage problem...
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Old Feb 7, 2004 | 07:31 PM
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Oops, thats what I meant
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Old Feb 8, 2004 | 12:35 PM
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3rd gen rear oil pressure regulator with shimmed front cover: At normal operating temp:

40 PSI @ idle
100+ PSI 3K RPM
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Old Feb 8, 2004 | 12:48 PM
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30 at idle, 60-70 on throttle.
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Old Feb 8, 2004 | 01:52 PM
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Originally posted by Rx7carl
30 at idle, 60-70 on throttle.
Same here.
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Old Feb 8, 2004 | 01:56 PM
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From: https://www2.mazda.com/en/100th/
Originally posted by Rx7carl
30 at idle, 60-70 on throttle.
yah me too, although it varies a bit day to day
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Old Feb 8, 2004 | 03:27 PM
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Under what conditions?

When the oil's cold, mine does 30 idle, 60 at cruise speeds (3000-up)

When the oil's hot, it does about zero idle, 30-45 at cruise.

That's not necessarily a bad thing... even at max power it's only making about 110-120hp so it's not punishing the bearings very much. Operating below the pressure regulator's popoff point just means that *all* of the oil coming from the oil pump is going through the bearings, and through the oil squirters, instead of most of it getting dumped overboard at the regulator. And at idle? Screw idle. Engine's making no power at that point, the loads are extremely minor, and you don't *need* oil pressure at that point.

It always gets me when people brag about how their megamondo oiling system pegs their gauge at idle. That's an awful waste of power trying to drive that oil pump....
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Old Feb 8, 2004 | 03:29 PM
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From: https://www2.mazda.com/en/100th/
Originally posted by peejay
Under what conditions?

When the oil's cold, mine does 30 idle, 60 at cruise speeds (3000-up)

When the oil's hot, it does about zero idle, 30-45 at cruise.

That's not necessarily a bad thing... even at max power it's only making about 110-120hp so it's not punishing the bearings very much. Operating below the pressure regulator's popoff point just means that *all* of the oil coming from the oil pump is going through the bearings, and through the oil squirters, instead of most of it getting dumped overboard at the regulator. And at idle? Screw idle. Engine's making no power at that point, the loads are extremely minor, and you don't *need* oil pressure at that point.

It always gets me when people brag about how their megamondo oiling system pegs their gauge at idle. That's an awful waste of power trying to drive that oil pump....
yeah mine made 0 at idle until i rebuilt the motor and found the passages clogged with silicon, bearings were ok
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Old Feb 8, 2004 | 10:18 PM
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Today (below freezing outside) the car started with 15psi while cold and once fully warmed up it was at 30psi. At 3k it is 60psi and will spike higher at higher speeds but not by much, 70psi max. I have Castrol 20W50 in the engine too.
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Old Feb 8, 2004 | 10:41 PM
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Normally your oil pressure should be a bit higher when your oil is cold, as it's thicker, thus creating more of a restriction. Technically your oil "pump" only creates flow, the lines, passages, and filter are what creates the pressure, so if the fluid doesn't flow well through them (Ie thick, cold oil) it creates higher pressure...
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Old Feb 8, 2004 | 11:15 PM
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also varies with new and old oil.

My readings change after an oil change
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Old Feb 9, 2004 | 06:03 PM
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Originally posted by Keaponlaffen
Technically your oil "pump" only creates flow, the lines, passages, and filter are what creates the pressure, so if the fluid doesn't flow well through them (Ie thick, cold oil) it creates higher pressure...
Makes me smile to read that...

Expounding further:

The oil pressure gauge is in the rear housing, pretty much at the beginning of the oil's trip through the engine. It's even before the oil filter.

Now, say you have 60psi.

- How much pressure is there after the oil filter?
- How much pressure is there at the main bearings?
- How much pressure is there at the rotor bearings?
(rotor bearings get their oil via the E-shaft, which gets its oil via the main bearings)
- How much pressure is there at the oil squirters?
(see above)

Now, thicker oil is harder to pump through a given passage, so there is a greater pressure loss at each given restriction. It doesn't necessarily lubricate better, it's just harder to pump.

Now you can get a glimpse into why I am a believer in thin oils... it goes through the passages easier, meaning less pressure loss through the various passages, meaning more oil where you want it. It also means less oil is being bypassed since it requires more volume flow through the system to generate a certain pressure; this means more oil is flowing through the bearings. *ANY* oil at all is sufficient for journal bearings, hell Hudson used splash lubrication well into the 50's. The positive-flow systems are there to flow oil through and take heat away. We have lots of heat to take away, so we need more oil flow.

Hey, I used to use 20W50 too, because everyone said to use it. Then I thought about it for a while... my next oil change will be with 5W20 oil.
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