Does Amsoil Signature Series 10w-30 have better cold flow than 0w40 version since it’s a much thinner oil? I know the whole W rating thing. Looking to consolidate into single oil for the home. 2021 Subaru Outback 2.5L and a 24 GMC Sierra 1500 5.3L. Both vehicles will see MN below zero temps. Particularly concerned about the cold starts but interested in 10w30 for shear stability since both cars are GDI.
Amsoil Signature Series 10w30 vs 0w40
- Thread starter Nuclear_42
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Patman
Staff member
There is no 10w rated oil that will ever perform better than a 0w rated oil in extreme cold
That would be completely dependent on the temperature.Below zero F the 0W would be better for cranking and pumpability. It’s not really about flow as such.
What is your specific concern about cold starts and GDI?
Absolutely correct.
I would think this statement should only hold true in the same grade. Like if you compare 0W-30 to 10W-30, I would absolutely agree with you. But when you compare 0W-40 to 10W-30 like the OP is doing, I disagree.
On the signature series as shown below, 10W-30 has a CST of 62.3 at 40C whereas the 0W-40 has a CST of 84.6 at 40C.
Am I understanding this wrong?
The winter rating when it is applicable at very cold temperatures is agnostic to the grade. That’s what Patman said and he’s correct.
An oil, any oil with a 10W rating is not appropriate for very cold temperatures. It may not pump.
An oil, any oil with a 10W rating is not appropriate for very cold temperatures. It may not pump.
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Note his use of the words "extreme cold". The Winter grade isn't relevant at 40C, but it certainly is at say -20C. If we use the "halving rule" (which is just a rule of thumb), the 0W-40 would be 1,515cP at -25C where the 10W-30 is 4,278cP.
Yep. Again I contend that the winter rating is one of the most misunderstood concepts on this site and just about anywhere. Both what it means and what it does not mean, and when.
Thanks, I missed the extreme part. That makes sense.
The CCS (Cold Cranking Simulator) is my go to, if provided, that'll clearly show performance at their respective temperature ranges. Obviously, the lower winter rating goes you'd want better results.
I was thinking like that until recently before I found out what CCS (Cold Cranking Simulation) means.
For example on the Amsoil PDS you posted above:
CCS for 10W-30 is 4278 cP at -25°C/-13°F
CCS for 0W-40 is 6062 cP at -35°C/-31°F
The difference is that 10W-30 cannot be pumped below -25°C/-13°F and the 0W-40 can be pumped down to -35°C/-31°F. Although the second one would be thicker at -35°C than the first one at -25°C.
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A long, long time ago, in a galaxy far, far, away (the 1970's), I had a 68 ford with a mechanical oil pressure gauge. Back then we all ran 10W-30 (non-synthetic of course, since it hadn't been born yet).
When started on very cold days, the oil pressure would take a long time (seemed like 20+ seconds) to register slowly on the gauge, THEN.... it would drop to ZERO
psi before coming back up and staying up.
And these older, carbureted engines had a high idle speed on cold startup.
I had always assumed that the oil pump emptied the oil pan of this thick viscous liquid before it could mosey it's way back down the engine and into the sump and oil pump pickup.
Pretty scary the first time I saw that happen. I guess that's why I always run a 0W-XX now.
When started on very cold days, the oil pressure would take a long time (seemed like 20+ seconds) to register slowly on the gauge, THEN.... it would drop to ZERO
psi before coming back up and staying up. And these older, carbureted engines had a high idle speed on cold startup.
I had always assumed that the oil pump emptied the oil pan of this thick viscous liquid before it could mosey it's way back down the engine and into the sump and oil pump pickup.
Pretty scary the first time I saw that happen. I guess that's why I always run a 0W-XX now.
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