Startup vis - sae30 vs 15w-40

[JonS]

I did some quick numbers on startup viscosity of sae 30 Delo 400 vs delo 15w40.

Temp sae30 15w40
59f 526cst 508cst
68f 367cst 364cst
77f 262cst 266cst
86f 192cst 199cst
95f 144cst 151cst
176f 21cst 25cst

Ths leads me to believe that 15w40 is no better than straight 30 weight oil at moderate temps. And that 30 weight would be more sheer stable at severe use. Wouldn't it?

 

[Pablo]

I believe you are correct at moderate temps. But what about colder?

Sheer stability may depend on the individual oil.

Remember though - the "labeling" is somewhat of a name game, too. IOW - Some 15w40's may meet a 10W-40 or close to a 5W-40....and the company will just call it a 15w40...or a SAE 30 could easily meet a 10w30 (this lends weight to your point)

 

[JonS]

At 32f
30 weight is 1840cst
15w-40 is 1634cst

 

[bulwnkl]

quote:

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Originally posted by JonS:
Ths leads me to believe that 15w40 is no better than straight 30 weight oil at moderate temps. And that 30 weight would be more sheer stable at severe use. Wouldn't it?

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Yes.
Most likely, yes.