Startup vis - sae30 vs 15w-40

[JonS]

I did some quick numbers on startup viscosity of sae 30 Delo 400 vs delo 15w-40.

Temp sae30 15w-40
59f 526cst 508cst
68f 367cst 364cst
77f 262cst 266cst
86f 192cst 199cst
95f 144cst 151cst
176f 21cst 25cst

Ths leads me to believe that 15w-40 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 15W-40's may meet a 10W-40 or close to a 5W-40....and the company will just call it a 15W-40...or a SAE 30 could easily meet a 10W-30 (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 15w-40 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.