Amsoil 0w-20 (ASM) vs. 5w-20 (XLM)

[ffxfina3]

I've got a specific question regarding these two oils from Amsoil. This specific questions pertains to their startup viscosities. Here is the data from Amsoil's webpages:

The 0w-20:
Viscosity @ 100°C, cSt (ASTM D-445) 9.0
Viscosity @ 40°C, cSt (ASTM D-445) 49.1

The 5w-20:
Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 8.5
Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 45.4

When I plug these numbers into widman's viscosity graph at:
http://www.widman.biz/Seleccion/Viscosidad/Conversiones/Graficos/graficos.html

It seems to show that Amsoil's 5w-20 is actually thinner in cold weather than the 0w-20 (even if only slightly). It shows a difference of about 200 cSt at -20 degrees celsius. Am I misunderstanding the Amsoil specs for these two oils? Shouldn't their 0w-20 be thinner than their 5w-20 at these low temperatures?

Thanks,
Bryan

 

[Pablo]

I think it's mostly a case of two points don't make a curved line.

The oils aren't that much different at normal temps (40°C!), but the ASM is a stouter base to start with, and then you must go much colder to see the real cold temp behavior. Compare the -35° and -30° cP's and especially the pour points and you will see the 0W is way better. -45°F vs -65°F

 

[ffxfina3]

Thanks Pablo!

 

[cdherman]

Of course, you should ask yourself, is my car going to see -35? Will I drive 15k miles on one OCI anyhow?

Perhaps the 5w20 is actually a better oil for me.....

 

[Craig in Canada]

Quote:

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Of course, you should ask yourself, is my car going to see -35? Will I drive 15k miles on one OCI anyhow?

Perhaps the 5w20 is actually a better oil for me.....

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Lower pour point has benefits that don't just apply if the ambient temperature is at that pour point. I believe those offering advice and quoting pour point were merely trying to urge you to use that as the third data point in addition to 40C and 100C viscosities to get an idea about the properties of the oil.

Instead of asking yourself whether your car will see -36, why not ask if it will see less than 40C. I bet it will, and the 20 weight that is thinner at even 10C will give you better startup flow and protection.

Of course both are probably fine, but the OP asked for a comparison, so here we are... If/when I ever get something that specs a 20, I'll be giving ASM a hard look.

Craig.

 

[Pablo]

Quote:

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Lower pour point has benefits that don't just apply if the ambient temperature is at that pour point. I believe those offering advice and quoting pour point were merely trying to urge you to use that as the third data point in addition to 40C and 100C viscosities to get an idea about the properties of the oil.

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Exactry.

And if the cold temp properties and shorter OCI's of the 5W-20 float your boat

then there is nothing wrong with that. In fact, it seems to fit the Honda OLM to a tee, to the point of me continuing to use the 5W-20 XLM in my personal stash until depletion, even though the ASM is just so tempting.