10 psi per 1000 rpm's?

[MarkJ]

Hey folks...new to the Board, but not entirely new to oil research...read the "Motor Oil 101" posting...very good info...gave me a missing piece to the oil puzzle.

Qusetions: Running 0w/30 M1 in my 2002 5.0 liter/V-8, which has a normal operating temp of 190. When warmed up it runs 40 PSI @ 55mph and 18 PSI @ idle. Based upon that rule-of thumb(10 psi/100 rpm)I am running high on both ends (even with 0/30 synthetic). Even though I don't have a tach, the idle is below 1000 and the over-drive at 55 is below 3000...maybe only 2500.

1) Is that rule-of-thumb true for all water-cooled street vehicles?

2) Is it possible that the engine is getting adequate "flow" even though the oil presures are the same as when I was running 5w/40 syn?

3) When its cold I get the same 60 PSI with the 0w/30 as I did with the 5w/40...what am I missing here?

Would appreciate any technical info to clear up these questions...in fact, if EHaas could weigh-in, that would be great too.

Thanx.

 

[Chris142]

18 psi @idle is plenty. In the old days oil lights used to flicker @idle because they only had 2-3 psi @ idle but those old 350's, 400's and 455's ran forever.

You get the same 60 Psi when cold because the pump has a bypass valve that won't allow more than 60 psi regardless of oil viscosity.

 

[MarkJ]

My concern with the idle PSI is that I have plenty of pressure but not enough "flow" (ie. the maxim of more pressure = less flow)???

I did not think about the bypass kicking in, but I guess I had hoped for a cold PSI below 60 with the 0w/30 synthetic...

I am learning as I go here.

 

[Steve S]

All is well with your engine and oil the higher readings. There is a problem with reading stuff and not really having the understanding of what is being read. The max readings with both oils could be the oil pumps bypass opening limiting the pressure? Cold oil always will have higher psi cause of the oil being cold.Use the recommended viscosity oils as in the owners manual "who warrants your engine?". Changed at a reasonable intervals depending on the oil is all you need to worry about . Make sure you are using a real good air filter and the intake plumbing is sealed as dirt is the enemy .

 

[Steve S]

Originally Posted By: MarkJ
My concern with the idle PSI is that I have plenty of pressure but not enough "flow" (ie. the maxim of more pressure = less flow)???

I did not think about the bypass kicking in, but I guess I had hoped for a cold PSI below 60 with the 0w/30 synthetic...

I am learning as I go here.
If there is enough pressure there is enough flow. Rule of thumb. Beware of the internet experts.

 

[mechtech2]

The 'rule' of 10 lbs pressure for every 1,000 RPMs is a gross over simplification. It is just a general basic idea, not an engineering concept.
You readings sound about right for a warmed up 30 w oil in a common V8.

 

[JADED]

Get yourself a Haynes manual, it will list all the minimum oil pressures at specific RPM's for your vehicle.

 

[alcyon]

I seem to get 10psi per 500rpm. At hot idle 950rpm at 93c its 18psi. Rev to 2000rpm its 40psi.
2500rpm 50psi. 3000rpm 60psi.

 

[3311]

I think that "rule" of 10 psi per 1k rpms has long since been retired. Are there any modern engines that idle at 10 psi when in good working order? .

 

[Clevy]

That idea was basically for small block bow ties on racing applications.

As far as flow is concerned a positive displacement pump moves the same volume of oil per rotation,so I doubt volume is a problem.
Whether you go thicker or thinner the only real change will be pressure. The pump moves the same volume of oil per rpm regardless of viscosity.

 

[Lubener]

This is a seven year old post. I doubt he has this car anymore.

 

[alcyon]

Originally Posted By: Lubener
This is a seven year old post. I doubt he has this car anymore.

true, but the information could be useful for others, instead of creating a new post.

 

[Festiva_Man]

from what i understood that 10psi/1000rpm is the MINIMUM before a rebuild. any less and your starving your engine, any more is fine. would be different on different motors, for example vtec may need more pressure to operate properly.