Rate of flow at low temperatures

[Bailes1992]

Originally Posted by Farnsworth
It's a good topic because there are so many who think thicker oil is better. Thicker can mean more relief valve opening, less flow to the engine, and more stress on the oil pump drive. Maybe this is obvious, but there are recurring posts of people over ruling their owners manual.


But that's only if you're picking to use an oil outside of the temperature ranges it and the engine you are using are designed for.

This entire statement by Shell is plain ridiculous, of course the 5w40 will flow better at -34°c, the 5w40 is designed to be usable down to -35°c and the 15w40 only down to -22°c. The 15w40 is well out of it's comfort zone!

As a general rule, thicker oils protect better and you should minimise the spread between the operating viscosity and winter rating to minimise the amount of VII's.

 

[OVERKILL]

Originally Posted by Snagglefoot
Originally Posted by Shannow
Originally Posted by JLTD
Where are all the "positive displacement" guys?

🦗🦗


Resaerch "MRV". pumpability. SAE J300...anything I've posted in the last 20years...and inform youself on why that advertising is made by the department of redundent information....

Yes, the pumps are PD...yourknowledge continues to be lacking, in spite of a couple of years of the same lacking in fundimental understanding jabs...


Typical Shannow. Starts with an attack. Yes, the pump is positive displacement, but the intake down in the sump is fed by atmospheric pressure and the oil is very thick. Cavitation is occurring. And even if it was not, typical oil pumps have a spring assembly and piston that will dump some oil back into the pan if the pressure gets too high. Where did you get your engineering degree? Honestly.


The purpose of the MRV test is to confirm that the oil can be drawn into the pump and... pumped. Demonstrating the characteristics of a lubricant outside the range it is supposed to be run doesn't do anybody any favours, and that's what Shannow is getting at.

Also, most oil pumps bypass internally, not back into the pan, just back into the inlet side of the pump. This usually isn't a huge relief, which is why it is possible to over-drive the oil pressure past the relief pressure on the pump, which I've observed numerous times with HV pumps on SBC's and SBF's.

I completely trust Shannow's credentials, and while he may be a bit abrasive at times, that doesn't undermine the knowledge and expertise he brings to the table. If you are put-off by the way he comes across, fine, attack the method not the man, taking shots at his credentials is absolutely idiotic.

 

[Shannow]

Originally Posted by Snagglefoot
Originally Posted by Shannow
Originally Posted by JLTD
Where are all the "positive displacement" guys?

🦗🦗


Resaerch "MRV". pumpability. SAE J300...anything I've posted in the last 20years...and inform youself on why that advertising is made by the department of redundent information....

Yes, the pumps are PD...yourknowledge continues to be lacking, in spite of a couple of years of the same lacking in fundimental understanding jabs...


Typical Shannow. Starts with an attack. Yes, the pump is positive displacement, but the intake down in the sump is fed by atmospheric pressure and the oil is very thick. Cavitation is occurring. And even if it was not, typical oil pumps have a spring assembly and piston that will dump some oil back into the pan if the pressure gets too high. Where did you get your engineering degree? Honestly.


The bait was cast...I respnded similarly...

You just happen to be on the recieving end when you ask similarly loaded questions...

Oh, UNSW, 1st clss honours, a decade in trubines, 30 years in power station engineering, and Commissioning an MDF plant, including hydraulics)

 

[Shannow]

Yes, pumps are positive displacement...assuming that the oil is un it's pumpable range, then it gets all the places that it needs to at the same time (no need to assume that a lower W grade gets theresooner, it doesn't)...put it below it's pumpable range, and it doesn't...that doesn't mean that a lower W is better...just choose an oil approprate for your condiditions...I could use SAE30 all year round (assuming they made one with the other specs required), and never have a pumpability issue.

I get annoyed with tests that are performed welland truly outside the realms of reasonableness for the grade,then presented as actually meaning something...e.g. where are all the postiive displacement guys...the Esso videos are similarly used to "trump"an argument when they ae simply mis-understood and misrepresented..

This shows that things fill and oil gets there about the same time FOR PUMPABLE oils...

Note that these two are a different J300, probably before the Sioux Falls type tests were added, based on pour point alone in those days.

This shows another of the problems....when it'stoo thin, you lose more in side leakage...note the thinner oil takes longer to get places (when beyond any normal semblence of operating temperture) - I got bitten by that on a hydraulic systems once that self heated too far...