Something I learned today!!

[deven]

I was just reading Dr. Hass' motor oil articles and i came across this...

It is time to introduce the concept of lubrication. Most believe that pressure = lubrication. This is false. Flow = lubrication. If pressure was the thing that somehow lubricated your engine then we would all be using 90 weight oil. Lubrication is used to separate moving parts, to keep them from touching. There is a one to one relationship between flow and separation. If you double the flow you will double the separation pressure in a bearing. The pressure at the bearing entrance is irrelevant.

In fact the relationship between pressure and flow is in opposition. If you change your oil to a thicker formula the pressure will go up. It goes up because the resistance to flow is greater and in fact the flow must go down in order for the pressure to go up. They are inversely related. Conversely if you choose a thinner oil then the pressure will go down. This can only occur if the flow has increased.

I always thought, higher the pressure then higher the flow.....just lets all you guys know how much i know about oil.

 

[Ferndog]

Something else to blow your mind - oil viscosity can change with pressure as well!

 

[Jim 5]

Interesting Ferndog, please elaborate!

 

[deven]

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Interesting Ferndog, please elaborate!

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http://www.noria.com/learning_center/cat...oup=Lubrication

 

[yannis]

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Something else to blow your mind - oil viscosity can change with pressure as well!

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Permanently?

 

[Al]

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This is false. Flow = lubrication.

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You have to be careful here. Flow is important in that oil must arive at the delivery points (bearings, cams, rings, chains, etc.) But once there, the oil must have the required viscosity to effectively function at those lube points. For instance, a .1 cSt oil @100C would be a wonderful thing in supplying the mains with oil, but once there the bearings would be toast. They need a 6 cSt oil.

 

[Toy4x4runner]

6 cSt

Stupid question, what does cSt mean?

 

[simple_gifts]

centistoke.

http://63.240.161.99/motoroil/104.html

 

[bruce381]

""If you double the flow you will double the separation pressure in a bearing.""

NO that is wrong flow to a bearing must be at a flow rate and viscosity to establish a HD wedge BUT to high a flow or too low a vis oil will disrupt that effect.

Doubleing flow will not always double bearing HD film BUT doubleing vis will.
bruce

 

[bruce381]

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Doubling flow will not always double bearing HD film BUT doubleing vis will.

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Well perhaps not double but increase is a better word
bruce