0w-30 and 10w-60 - same pour point?

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So I'm looking at Castrol's specs for their SLX (GC) 0w-30 and their RS 10w-60, both fully synthetic as far as we know. Both have a pour point of -57C. Does this seem right or is this some number tinkering on Castrol's part?
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Pete, I think it is possible to have the same PP and different winter cold-cranking rating because it is an actual cranking test with a simulated load. The friction modifier content could be difference. Just a guess though, if they had the same base oil.
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Winter rating is subject to the blenders desire to obtain the lower rating by attempting to pass a given test as well. -Audi Junkie
 
Right, cold performance is measured by the MRV BPT (Mini Rotary Viscometer Borderline Pumping Temp) test. The specs are part of SAE J300.

The test determines the "yield stress" of the oil, which happens at 60,000 cP. A few years back, the number used to be 30,000 cP, not sure why it changed.

The CCS (Cold Crank Simulator) is also of limited usefullness. They measure the CCS in Poise or cP at -30 C, -35 C, and -40 C. So what, what happens once the motor is running??

Beyond 600 Poise, oil refuses to flow into the pickup tube and the oil pump runs dry. This temp is usually a good deal ABOVE the rated pour point. Once the oil turns solid, something has to give.

Around here, I've seen cars running a regular 5W-30 get jump-started at -42 F and the oil pump drive has sheared. Stands to reason, if the oil has turned solid, how can the gears inside the oil pump turn??

Actually, pour point has no mention in J300 and is NOT part of the test. I guess that's so you know at what temp the oil needs a hammer and chisel to get out of the bottle.

I run Mobil 1 0W-30 in winter as its MRV BPT is -58 F, though the HTHS is awful thin. In summer I switch to Mobil 1 10W-30, to get the better HTHS.
 
heyjay, how can you bea junior member and know so much?
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This is my third winter in northern PA where low winter temps has been an issue. I learned a lesson last week when my woman's I-5 Audi with 10w-30 froze up good at -5 degrees. I used a hill and push-started it, tough to spin the engine but it started...hope I did not damage it.
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A total novice scale I made up for idiots is "don't use a (multiweight) oil at temps below what the w-rating says", for example a 10w should not be used under 10 degres F and so on to a 0w oil at zero degrees F seems to reflect what happens anyway. Not many car owners are as knowledgable as you, and are slow to comprehend anything more basic than I discribed ...duh... centipoise?
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Actually a 5w will get you down to about -20, with the 0w being used after that.
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Ask me how I know...

That doesn't mean a 0w won't help in the 0 to -20 range - it will, just not entirely necessary.
 
Thank you for the welcome. I had to learn the "hard way" running commercial equipment for 22 years. Finally gave up on listening to idiot salespeople and got the Big Book Of Instructions straight from the horses mouth. I was just refered to this site from the GM Trucks forum by an Amsoil dealer there. I'm happy to have joined!

Although the SAE J300 test has basic requirements for a 5W-x and a 0W-x, these are "ballpark" and only real MRV BPT testing will tell you what the oil is capable of doing. For example, Mobil markets a 0W-30 in Europe that meets the new VW 506.x requirement: it's pour point is -39 C and the BPT is -34 C. That wouldn't work very well where I live.

Regarding your woman's Audi, I'm not aware of any 10W-30 oils that meet the VW-Porsche-Audi service spec. Maybe Mobil 1, but their 10W-30 has a BPT of -42 F so it should have been fine at -5 F.

For your sake and happy matrimony, I also hope you didn't bugger it up, the couch is a cold and uncomfortable place to spend the winter!

Well, maybe the cat can snuggle up and keep your footsies warm!
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I don't pay attention to "pour point" as it has no relavance to lubrication. Due to the extreme cold temps here, I only look at what the MRV BPT rating is: the lower the better.

My 2000 GMC Sierra with Vortec 5.3 appears quite sensitive to an oil's BPT, which is why I use Mobil 1 0W-30 in winter. I figure the slight increase in wear resulting from the lower HTHS is MORE than made up for in better cold wear protection: instant oil pressure at -42 F.

I use Delvac 1 in my commercial equipment and even at -42 F, instant oil pressure. Have to like that!

Jerry

quote:

Originally posted by TSoA:
heyjay, how can you bea junior member and know so much?
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This is my third winter in northern PA where low winter temps has been an issue. I learned a lesson last week when my woman's I-5 Audi with 10w-30 froze up good at -5 degrees. I used a hill and push-started it, tough to spin the engine but it started...hope I did not damage it.
dunno.gif
A total novice scale I made up for idiots is "don't use a (multiweight) oil at temps below what the w-rating says", for example a 10w should not be used under 10 degres F and so on to a 0w oil at zero degrees F seems to reflect what happens anyway. Not many car owners are as knowledgable as you, and are slow to comprehend anything more basic than I discribed ...duh... centipoise?
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Heyjay has some good first-hand info.
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I've run Syntec and M1 10-30 year round and both seem fine at -5F, no problem.

I somewhat ignore pour point specs. unless they are extremelmy high temp. CCS seem pretty relevant.
 
Maybe I should just move to a part of North America that NEVER sees a temp of -30 F or colder??

Yep, been hard-learned experience that taught me how crappy some oils perform at their limits, especially the cold limits.

Although the SAE J300 is a good starting point, the SAE oil standards are so lame as to be almost worthless. Remember, if a 5W is supposed to be "good" at -35 C, that means it has reached its pumping LIMIT at -35 C. It was probably marginal at -25 C.

CCS is somewhat redundant. If the oil is thin enough to flow at say -40 F, it will certainly be easy enough to crank. Of course, the motor can crank and yet the oil be too thick to properly flow.

Another reason why I don't trust "pour point:" how do you define "pour?" Like water? Like taffy? Say you tip a beaker of 30 oil that has been kept at -20 F outside. Go for lunch. When you get back, the oil may have finally ooooooozed out of the beaker. So is the "pour point" -20 F?

Some more good advice: if you ask your oil supplier picky questions about HTHS and MRV BPT and you get that "deer in the headlights" look from him, take a fast walk. You do NOT want to give him your money OR trust that your $$$ commercial equipment will be properly lubricated.
 
That's what they say.
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I am not even going to attempt 10w again in winter. Pennzoil HMV 10w-30..it is thick.

FTR- it is an 18 year old Audi, I was not worring about using in-spec oil anyway. Now it has Belgium Syntec 5w-40 and it started up at 0 degrees fine.
 
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