Positive displacement oil pump

[Jeep Junkie]

They say our 3.6 has positive displacement oil pump. It is like it doesn't depend on how thick or thin the oil is. As long as oil is pump-able, the oil pump takes like say 0.5 quarts of it and forces it into the engine. So oil gets into the engine at the speed of the oil pump, not the speed of oil flowing on its own. Is that all true? If it is true, then what difference does 0w or 5w or 10w make? Because all those three are pump-able in at 30 degrees F. It would only make a difference if you are in -40 degrees and 10w isn't pump-able at all.
No wonder some critisize those oil cold flow tests on youtube because oil pump is not involved in those tests.

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[Jeep Wick]

They say our 3.6 has positive displacement oil pump. It is like it doesn't depend on how thick or thin the oil is. As long as oil is pump-able, the oil pump takes like say 0.5 quarts of it and forces it into the engine. So oil gets into the engine at the speed of the oil pump, not the speed of oil flowing on its own. Is that all true? If it is true, then what difference does 0w or 5w or 10w make? Because all those three are pump-able in at 30 degrees F. It would only make a difference if you are in -40 degrees and 10w isn't pump-able at all.
No wonder some critisize those oil cold flow tests on youtube because oil pump is not involved in those tests.

The viscosity makes a big difference. Look at the GM engines that are failing...the fix, for now, is a thicker oil. Watch @themotoroilgeek on youtube. The thicker oils have a higher shear rating, which is very important.

 

[Jeep Junkie]

The viscosity makes a big difference. Look at the GM engines that are failing...the fix, for now, is a thicker oil. Watch @themotoroilgeek on youtube. The thicker oils have a higher shear rating, which is very important.

No, what I meant is that PD oil pump doesn't care if oil is thin or thick, it pumps them with equal speed. So people who say that thick oil during cold start flows slowly and engine is hurt, that logic doesn't make sense. It would only make sense if oil was left to flow on its own, obviously in that case 0w20 would out flow a 10w30.

 

[Erievon]

I'm no engine genius, but my thought is there's only one oil pump. If that's true, once the oil pump spits it out, how far and how quick it gets downstream away from the pump would depend on the thickness. I don't think the whole system is pressurized so to speak.

 

[Old Dogger]

The oil pump is only one part of the equation. So, let's just say that the oil pump is capable of pumping 0W AND 10W at about the same speed. But here is the catch, the oil next has to flow through orifice size holes to the VVT and lower end components, that need lube to function. The sizes needed, are engineered into the castings. So based on this, thinner engine oil will flow faster than thicker oil. The needed sizing of the casting holes has been engineered, for what is needed.

 

[Jeep Junkie]

The oil pump is only one part of the equation. So, let's just say that the oil pump is capable of pumping 0W AND 10W at about the same speed. But here is the catch, the oil next has to flow through orifice size holes to the VVT and lower end components, that need lube to function. The sizes needed, are engineered into the castings. So based on this, thinner engine oil will flow faster than thicker oil. The needed sizing of the casting holes has been engineered, for what is needed.

I see

 

[GW’s JL]

All oil no matter the grade is to thick at cold starts. The “W” or winter rating is the pumpability of an oil and is what you look at in choosing an oil for cold starts. A 0W-20 and 0W-40 perform the same.

Below is the official explanation.

“Dynamic viscosity is measured by the Cold Crank Simulator (CCS) test (ASTM D5293). Dynamic viscosity determines an oil’s low-temperature, winter or “W” viscosity rating — the “5W” in 5W-30 motor oil. The lower the “W” rating, the faster the oil flows when cold and the easier it is for the engine to turn over when starting.”

 

[Jeep Junkie]

The oil pump is only one part of the equation. So, let's just say that the oil pump is capable of pumping 0W AND 10W at about the same speed. But here is the catch, the oil next has to flow through orifice size holes to the VVT and lower end components, that need lube to function. The sizes needed, are engineered into the castings. So based on this, thinner engine oil will flow faster than thicker oil. The needed sizing of the casting holes has been engineered, for what is needed.

But in your climate in Arizona, it's not a big deal, 5w30 will be like 0w-20 at 10 degrees lower temperature. Not a big deal for me either in the summer, but in the winter I will run PUP 0w20. This morning when I started the Jeep, oil temperature was already 70°. So my PUP 5w30 behaved like 0w20 at 50 degrees, no biggie.

 

[Pape]

The oil system in a car is the same as the white water system in a city or a house.
You have a pump tha push it in the piping and you have various path and exit of different size.
The argument about oil thickness is too tick can be detrimental when cold for certain small passage reducing the needed oil flow. Just like in a water system oil will take the path of less resistance.

Also have a look at how winter grade are tested as it is not the same as operating grade test

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