Does pour point really matter?

[airbus]

Where I live winter temperatures quite often reach -30 celcius. My car does not have a block heater,not that it would matter anyways because my car sits parked at the airport (travel alot) most days. I currently use Mobil 1 0w20 that has a pour point of -57 degrees celcius! I think most conventional oils are in the -25 to 30 range. Obviously my car will start better with Mobil 1 vs conventional oil but does anybody notice (uoa) significantly lower uoa wear numbers in the winter using an oil like Mobil 1 with a low pour point?

 

[Ray H]

Pay more attention to actual pumpability limit numbers. Pour point only reflects gravity's influence on oil flow after about 5 minutes into the test.

 

[Ugly3]

AS I recall the actual pumpability of a motor oil is 15 to 20 degrees above the pour point. With a -57 pour point and actual temps of -30 you are right near the limit of the protection the oil can offer you.

I have looked all over and can not find an oil with a materially lower pour point (several are within a degree or 2).

I have noted that most viscosity charts stop at -30.

 

[Jay]

I've never read the ASTM D 92 protocol for pour point, but it must be very subjective judging from all the funky pour point specs I've seen. Cold Cranking and Cold Pumping viscosity are the two important cold temperature tests to look for. There's some disagreement in the industry over which is more important and where the limits should be set, but there's not much disagreement that these are the important tests.

 

[TC]

I always thought that Borderline Pumping Temp (ASTM D-3829) is what cuts to the chase. It's pretty straightforward: "Predicts the lowest temperature at which a motor oil can be continuously and adequately supplied to an engine's components." Pour Point (ASTM D-97) simply indicates how fast chilled oil will move along a test bed's incline. Both BPT and PP degrade over time, of course, so such spec's only apply to brand-new oil.
http://www.bestchoice-car-care.com/american-society-for-testing-and-materials.html

Borderline Pumping Temps appear to be similar between various brands of conventional oils. BPTs, per their spec sheets, for Pennzoil Conventional multigrades:
5w-20: -31F
5w30: -31F
10w-30: -22F
10w-40: -22F

 

[Blue99]

Actually, -30C converts to -20F and I would imagine alot of the airport rental cars with conventional 5w30 oil are starting at this temp!

As RayH indicated, the Cold Cranking Viscosity per ASTM 5293, is a good measure of the cold temp performance of an oil.

Per the SAE J300 viscosity charts:

code:

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0W 6200 max cP at -35C (-29F)

5W 6600 max cP at -30C (-20F)

10W 7000 max cP at -25C (-11F)

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Some conventional oils with excellent cold start performance are rated 3600-4200 cP for the 5W viscosity range.

If any low temp data exists where the viscosity of the oil prevents the starting of a vehicle or the oil can no longer lubricate, I'd certainly be interested in seeing it!

 

[TheFuror]

quote:

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Originally posted by Ray H:
Pay more attention to actual pumpability limit numbers. Pour point only reflects gravity's influence on oil flow after about 5 minutes into the test.

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I know that GM has a low temp pumpability standard for 5w30 and 10w30 (GM 6094M), which is more stringent that SAE/API standards. The oils I have looked at meet this standard (Castrol, Mobil, and Kendall are the specific brands I asked).

Bob W.