Help me understand @40c cSt, @100c cSt, viscosity

[blue_goose]

Trying to learn more more about 0w20 oils and by reading some posts here I take it that a lower @40c is better when it comes to colder weather? I've been reading some MSDS sheets on oils I'm considering and they read as

Pennzoil Platinum 0w20 40c 46.8
100 c 8.6
Viscosity 164

Royal Purple 42.58
8.37
177

Mobil 1 Advanced Fuel Economy 44.8
8.7
173

Quaker State Ultimate Durability 42.6
8.39
175

Valvoline Synpower. 47
8.8
169


Amsoil Signature Series. 49.1
9


TGMO 36.1
8.5


By looking at this info should I be able to tell which would be a better flowing oil at lower temps?


Or to break it down further, what do these numbers mean and should it matter to me?

Thanks

 

[gregk24]

Its kind of a measurement of thickness at a certain temperature. TGMO is the thinnest of all of those at start up (that is good), and is plenty thick enough when at operating temp.

 

[901Memphis]

Your missing the viscosity index of Toyota which is over 200. The Toyota is a pretty good winter oil.

 

[blue_goose]

The MSDS sheets I looked at did not have the viscosity ratings for Amsoil or the TGMO.


So just judging by the numbers here the Royal Purple, Quaker State Ultimate Durability and the TGMO look pretty good. I have about 8 quarts of TGMO and also a 5 qt jug of the RP on order. The Quaker State Ultimate Durability is readily available and looks like the sleeper of the group maybe?

Perhaps I am over simplifying things by just using these numbers but that's why I'm asking

 

[RamFan]

Wait 'til Caterham hears of this and bring HTHS into the equation.

 

[Danh]

40 degrees centigrade is still pretty warm so this value alone doesn't really tell you how an oil performs below freezing. Even the VI index is only a mathematical representation of the change in cSt between 40C and 100C and an oil can have different characteristics at much lower temps.

It's easy to overthink this. For decades cars in cold climates survived quite nicely on 10w-40 and 20W-50 conventional oils. Any of the 0W-20s you mention will work really well for you and unless you move a thousand miles north I doubt your engine would really notice a difference.

 

[Quattro Pete]

Originally Posted By: Danh
40 degrees centigrade is still pretty warm so this value alone doesn't really tell you how an oil performs below freezing. Even the VI index is only a mathematical representation of the change in cSt between 40C and 100C and an oil can have different characteristics at much lower temps.

Agreed. At very low starting temps, values such as CCV and MRV become more important.

 

[dparm]

KV values aren't that useful, as it's just two points on a curve. Your oil doesn't even spend much time at those temps -- it's why HTHS is more useful.

 

[blue_goose]

Ok so that leads me to the next question then.....what is HTHS and how is that read and for what purpose?

 

[Merkava_4]

Originally Posted By: Danh
40 degrees centigrade is still pretty warm so this value alone doesn't really tell you how an oil performs below freezing.


Centigrade? I thought it was suppose to be Celsius.

 

[Danh]

Originally Posted By: Merkava_4
Originally Posted By: Danh
40 degrees centigrade is still pretty warm so this value alone doesn't really tell you how an oil performs below freezing.


Centigrade? I thought it was suppose to be Celsius.

The Centigrade tesession frequently used by the U.S. scientific community while Celsius is used pretty much everywhere else. They mean the same thing - guess I just reverted to high-school physics. Maybe it's safer to just use "C".