Oil Viscosity vs. Oil Pressure

[blackdiamond]

What connection is there between oil viscosity and oil pressure? The engine in question is a 20r/22r hybrid that is driven like a race car. The owner indicated that 20w-50 wasn't cutting the mustard and the reason was that it wouldn't hold oil pressure at high rpm. At some point it seems that the oil pump wouldn't be able to keep up with the higher viscosity.

Any thoughts?

 

[GMorg]

Exactly what does "hold oil pressure" mean in this context? Are you saying that oil pressure would not continue to rise or that oil pressure would actually drop at high RPM?

 

[AITG]

On a theoretical level, pressure is the result of resistance to flow. Thinner fluids flow more easily, therefore less pressure is required to move them. Larger clearances result in less resistance, therefore less pressure will be required to move a given volume in a given time.

Practically, thicker fluids may result in more pressure but less flow. Worn components result in lower pressures but increased flow.

AFA the racer is concerned: I have no idea what he was getting at - sorry.

 

[sm00thpapa]

This should answer your question

 

[ltslimjim]

Originally Posted By: sm00thpapa
This should answer your question

 

[AEHaas]

One reason may be that the oil pump bypass pressure is set too low for your application / oil grade combination.

The later chapters below may illustrate the issue:


http://ferrarichat.com/forum/faq.php?faq=new_faq_item#faq_haas_articles

Original (but edited by others) version:

http://www.bobistheoilguy.com/motor-oil-101/

aehaas

 

[mechtech2]

It could be too much heat, which can require a thicker oil to keep the pressure up.
But if an engine needs more than a 50 [which you have], it is extreme, for sure.

 

[aquariuscsm]

If you need a thicker than 20W50,there`s always a mono grade 50 or 60.

 

[A_Harman]

Originally Posted By: blackdiamond
What connection is there between oil viscosity and oil pressure? The engine in question is a 20r/22r hybrid that is driven like a race car. The owner indicated that 20w-50 wasn't cutting the mustard and the reason was that it wouldn't hold oil pressure at high rpm. At some point it seems that the oil pump wouldn't be able to keep up with the higher viscosity.

Any thoughts?


Maybe the 20w50 is TOO thick. The higher viscosity oil will drain back to the pan more slowly than a 5w30, making it more likely that the pickup will starve for oil during hard acceleration or cornering. How much oil pressure is it maintaining at high rpm? Under what driving conditions is the oil pressure dropping?