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What is the ideal oil pressure? #5411280 04/23/20 01:54 PM
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ApexEight Offline OP
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I've read the general rule for ideal oil pressure is 10 PSI for every 1K RPM, at operating temperature, as seen in RAT 540's blog: https://540ratblog.wordpress.com/

Then there is this article that gives a wide range of 25 to 65 PSI at operating temperature, but does not specify at what RPM: https://www.carbibles.com/high-oil-pressure/

What is the ideal engine oil pressure at operating temperature at both idle and redline?

Re: What is the ideal oil pressure? [Re: ApexEight] #5411281 04/23/20 01:58 PM
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demarpaint Offline
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That's a "general rule" but a better more specific guideline for oil pressure would be for what specific application? Ideal oil pressure for my 1988 4.9L Ford engine might not be so ideal for a modern engine.


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Re: What is the ideal oil pressure? [Re: ApexEight] #5411293 04/23/20 02:07 PM
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10psi per 1k rpm is a good general idea. My Pentastar can ramp itself up to 90+psi, otherwise it cruises around at ~30psi. The 5.7 is always between 50 and 60psi.


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Re: What is the ideal oil pressure? [Re: ApexEight] #5411294 04/23/20 02:10 PM
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It is a rule of thumb.


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Re: What is the ideal oil pressure? [Re: Skippy722] #5411295 04/23/20 02:12 PM
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In today's applications , most oil pumps are Variable Pressure so it is not related to RPM alone or load .

Re: What is the ideal oil pressure? [Re: ApexEight] #5411297 04/23/20 02:15 PM
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find out what toyota does - their engines last a long time.


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Re: What is the ideal oil pressure? [Re: ApexEight] #5411308 04/23/20 02:26 PM
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skyactiv Online Content
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Find out what Honda does, they have the lowest percentage of engine failures under warranty.


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Re: What is the ideal oil pressure? [Re: ApexEight] #5411314 04/23/20 02:31 PM
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Oil pressure is better described as hydraulic fluid. You can not compress fluid but past the dam of bearing surface and the seal surface is ambient air pressure. You can put too much pressure on the seals, so the oil pump has a bypass. The thicker oils will have the bypass open up with a bit less flow which will also mean a raise of temp.

Many new oil pumps are set up like this.

https://www.hexorcism.com/16ND/sh13083/

2 step oil bypass and controlled by engine inputs.

Last edited by Bill_W; 04/23/20 02:32 PM.

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Re: What is the ideal oil pressure? [Re: ApexEight] #5411317 04/23/20 02:37 PM
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My Z71 might be at 30 psi sitting at a red light … and 70 psi if I’m passing someone … both are ideal pressures from a variable displacement oil pump …

Re: What is the ideal oil pressure? [Re: ApexEight] #5411319 04/23/20 02:39 PM
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Ask Scotty Kilmer

Re: What is the ideal oil pressure? [Re: walterjay] #5411321 04/23/20 02:40 PM
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He will need you to rev up your engine first 🤪

Re: What is the ideal oil pressure? [Re: ApexEight] #5411336 04/23/20 02:55 PM
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Check the service manual. Oil pressure changes with oil viscosity, temperature and RPM. If the oil pressure is low when using the correct viscosity and it's at the normal operating temperature (and the pressure sensor is known to be good), then it means there's a mechanical problem (ie, worn pump, worn bearings, etc).

You can have the same oil flow (positive displacement oil pump) but with low oil pressure, which means the flow path has become less restrictive - ie, worn journal bearings.

Re: What is the ideal oil pressure? [Re: ApexEight] #5411377 04/23/20 03:52 PM
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It may be interesting to note that connecting rod bearings, arguably the most critical bearings in an engine, may only receive intermittent pressurized oiling.

In many engines, the upper main bearing has a groove, that allows oil flow. The lower main bearing often has no groove, so there is no flow through the drilled crankshaft and into the rod bearings, when the crankshaft hole is not adjacent to the groove.

In years past, some connecting rods had no oil pressure feed, and used a "dipper" that would scoop oil from a curved trough. Some industrial diesel engines used splash lubrication to fill a scoop on the top of the rod bearing and gravity would get the oil in. Of course, lawn mower engines often don't have any form of oil pressure to the connecting rod.

[Linked Image from secureservercdn.net]

A chevy rod "dipper" from the '40's

[Linked Image from chevsofthe40s.com]


Originally Posted by skyactiv
Find out what Honda [and Toyota] does, they have the lowest percentage of engine failures under warranty.


They use very high quality (well refined and often lighter) parts with superb metallurgy, machined to exacting tolerances, with precise fits. They also balance engines exceptionally well. In years past, it was obvious to a 4 year old child that Honda engine parts were higher quality than Chevy engine parts. Today, the difference is not quite so "self evident", but it still exists in many cases.

Also of note, in years past on many small Honda engines, rod bearings were seemingly as large in diameter as the pistons themselves.

Last edited by Cujet; 04/23/20 04:06 PM.

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Re: What is the ideal oil pressure? [Re: ApexEight] #5411479 04/23/20 05:59 PM
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I would say the idea pressure is one that isn't low enough to damage the engine, but also isn't high enough to rob power.


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Re: What is the ideal oil pressure? [Re: bdcardinal] #5411487 04/23/20 06:06 PM
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Originally Posted by bdcardinal
I would say the ideal pressure is one that isn't low enough to damage the engine, but also isn't high enough to rob power.


That's likely the most accurate answer. Many race car (and piston aircraft) "low oil pressure" events are generated by excess heat, not insufficient flow.


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