15-40 thicker than 30w

[JonS]

Using the viscosity calculator i found, it seems that:
-15w-40 Chevron Delo is 1089 cst at 50f
-30w Delo 400 is 744 cst at 50f.

It isn't until you get to 0f that they are the same cst of about 1770 cst.

This would mean that 30w would be better in cold weather - right?

 

[Dr. T]

No the 15W is better than a 30W as is everything else with a lower 'W' number.

Are you referring to a straight 30 weight? How can it be even usable at 0F?

 

[JonS]

The viscosity of a straight 30w is the same as a 15w-40 at 0f (1750)
I used this

http://www.geocities.com/CapeCanaveral/3655/VI.html

 

[KJA426]

The only thing I know concerning this issue is that HD 30 isn't recommended for anything under 40F. 15w-40 would probably pump down to -20F.

 

[TallPaul]

I don't believe there is a "30w" category. I think you mean straight 30 weight, the "w" being reserved for winter ratings. A straight 30 might pass the 20w test. So in general the 15w40 will be better of the two in colder weather.

 

[JonS]

quote:

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Originally posted by TallPaul:
I don't believe there is a "30w" category.

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I meant straight 30 weight not 30w.