If all oil is too thick when cold...

[ZeeOSix]

Agreed the positive displacement (gerotor or lobe or gear) is at the pump proper, and the pump must lube itself, but that isnt it's purpose. It is to lube plain bearings and component proximal and distal in the engine proper through discharge, but will be limited in ability to move lubricant volume by the viscosity of the fluid when bypass is initiated. Volume flow though a restricted orifice at constant pressure will be lessend with increasing viscosity.

What's that got to do with your statement in post #55 of: "... these positive displacement pumps are all but a thing of the past in passenger cars, as engineers/designers look to improve parasitic losses in engines."

The oil pumps in modern cars still move the same volume of oil regardless of viscosity (as Shannow mentioned) just like the old time PD pumps do if not in pressure relief.

 

[Bryanccfshr]

I was actually pointing out the additives percentage, which is 20% and includes VII load, versus 18% for the 0w-30 displayed in 4WD's chart.

I see your point about the minimal difference, I was being a bit esoteric. the differences are getting to be minimal

 

[wpod]

Will the oil flow from the sump when it is cold? Think of sucking a thick milkshake through a straw as compared to milk.

 

[ZeeOSix]

Will the oil flow from the sump when it is cold? Think of sucking a thick milkshake through a straw as compared to milk.

See the video in Post #58, and watch from the 8:00 mark which shows what happens.

 

[ARCOgraphite]

Some pickups are a foot away from the pump, some are closer, some pumps are in the oil.
Likey will see varied results with oil gelled or near the gel point.
No Sub for heated block and sump in extreme cold weather

 

[OVERKILL]

Some pickups are a foot away from the pump, some are closer, some pumps are in the oil.
Likey will see varied results with oil gelled or near the gel point.
No Sub for heated block and sump in extreme cold weather

That's the whole point of the MRV test however, to determine pumpability.

 

[Jimmy_Russels]

The number of (incorrect) assertions, speculation and generalizations made here is truly incredible.

1. As long as the oil isn't past the pumping point, it will start pumping immediately. That's one of the main purposes of the Winter rating.

2. Oil pumps are positive displacement, so unless the pump is on the relief, it is displacing the same amount of oil whether it's 0w-16 or 15w-40

3. A 0w-30 does not have "way more" stuff in it, which by "stuff" I assume you mean VII. It may have a higher percentage than a synthetic 10w-30, but then it may not. It will depend on the base oil blend of the product. 10w-30's are usually blended with cheaper bases because they don't need to meet the cold temperature requirements that a 5w-30 or 0w-30 has to. Those bases may actually be thinner, depending on the base oil selected, like Group II for example.

4. No, high compression engines do not do more damage to oil. Honda's S2000 engine had no exotic oil specs nor have myriad other engines with high compression ratios, including Mazda's Skyactiv engines. Engines with a million feet of timing chains have a higher propensity to shear VII polymers.

5. There are myriad factors that determine how long a given oil can be run including sump size, fuel dilution, oil temperature, short tripping or non....etc. Semi's run very long
OCI's despite being under heavy load for a significant duration of their operating cycle because they have excellent filtration and massive sumps. A car that's short-tripped under very light load can destroy the oil in a much shorter period of time than the same car with higher average load that's operated for long commutes every day.

Immediate pumping does not equal fluid flow. A cold engine that cranks slower because the oil is thick and has massive parasitic drag means very little fluid flow. The thinner oil will have less drag and as such the engine can crank faster allowing for the fluid (oil) to reach where it needs to go faster.

Sure, if the cranking is 2rpm for both oils at the cold temp, then we should expect about the same fluid flow under assumption of incompressible fluid.

And yes, a 0w has way more VII in it than a 10w or 15w.

 

[Bryanccfshr]

Immediate pumping does not equal fluid flow. A cold engine that cranks slower because the oil is thick and has massive parasitic drag means very little fluid flow. The thinner oil will have less drag and as such the engine can crank faster allowing for the fluid (oil) to reach where it needs to go faster.

Sure, if the cranking is 2rpm for both oils at the cold temp, then we should expect about the same fluid flow under assumption of incompressible fluid.

And yes, a 0w has way more VII in it than a 10w or 15w.

If you are using time to measure speed, then yes. But if you are using engine revolutions to measure oils being pumped to the furthest point they are equal.

 

[OVERKILL]

Immediate pumping does not equal fluid flow. A cold engine that cranks slower because the oil is thick and has massive parasitic drag means very little fluid flow. The thinner oil will have less drag and as such the engine can crank faster allowing for the fluid (oil) to reach where it needs to go faster.

Sure, if the cranking is 2rpm for both oils at the cold temp, then we should expect about the same fluid flow under assumption of incompressible fluid.

And yes, a 0w has way more VII in it than a 10w or 15w.

Immediate pumping does in fact mean flow. A positive displacement pump displaces the same amount of oil per revolution, so if it is pumping, it is moving fluid.

As soon as the engine fires, RPM is going to be basically identical. No engine is going to fire at 2rpm, that's the whole purpose of the CCS testing parameter, to ensure the engine starts. Flow before the engine fires, which will be the same for a given RPM, is of no consequence, it's flow under fire; flow when the engine starts, when there's actually load on the connecting rod bearings that's important, and that will be the same within the given suite of caveats about oil bypassed through the relief as mentioned.

And no, a 0w-xx does not universally have more VII in it than a 10w-xx or 15w-xx, you are just manufacturing facts again. 4WD and myself both posted blending excerpts that highlighted that fact. Again, you claiming it so doesn't make it true.

 

[DGXR]

Oils are designed to cover a range of viscosities and a range of ambient temperatures, and nearly all applications have a margin of safety built in. That's why we have the proverbial oil chart that shows 5+ different multi-vis oils covering a range of temperatures, and many of them are overlapping. The "correct" or "best" viscosity is not a black & white answer.
If a 10w30 will work in my 30F+ winter temps, why would I run a 0w30? Especially when my summer temps can be 105F+ for weeks at a time? Not that it would matter much for the reasons previously stated, but I personally would prefer a 10w30 over 0w30 in my typical seasonal temps.