HTHS observations.

[splineman]

I usually use Delvac MX 15w-40 in my 2005 sportster but was in the local parts store and they didn't have any.
I bought Castrol Activ 4T 15w-50 instead, as recommended by Castrol.
What i found interesting is that the 15-40 Delvac has an HTHS of 4.3 and the Activ 4T 15-50 is 4.1.
This is even though the 40 and 100 deg viscosities of the Activ 4T 15-50 are quite a bit thicker than the Delvac MX 15-40.
Am I correct in saying the 15-40 Delvac holds up better in an operating engine and is therefore actually thicker in operation?
Cheers

 

[Shannow]

Yep, spot on

 

[sunruh]

friends dont let friends use castrol gtx

 

[LoneRanger]

Could also just be the way Castrol publishes HTHS numbers on their products. Often, they don't tell the actual tested HTHS but instead they show the API min spec HTHS for that viscosity.

 

[Shannow]

Originally Posted By: LoneRanger
Could also just be the way Castrol publishes HTHS numbers on their products. Often, they don't tell the actual tested HTHS but instead they show the API min spec HTHS for that viscosity.


If that was the case, it would be >3.5, or "3.5 min" like they often do.

One would assume that by putting an actual number it has relevance.

 

[Robenstein]

Originally Posted By: sunruh
friends dont let friends use castrol gtx


BP ownership has taken a pretty bad toll on the Castrol brand. It used to be a very fine line of products, but now there are only a few good products left. I got a 5 quart jug of GTX Magnatec. Been using it for my snowblower and other gas powered implements where I need a 30 weight oil.

 

[splineman]

I still find it interesting that viscosity # is not the whole story and the 15-40 is apparently more robust in service but thinner at startup than a 15w-50.
A friend uses shell hx3 20w-50 in his bike and its very reasonably priced but no hths figures I can find so have avoided it.
Castrol may not be what they were but they aren't shy to charge.

 

[Geonerd]

Originally Posted By: LoneRanger
Could also just be the way Castrol publishes HTHS numbers on their products. Often, they don't tell the actual tested HTHS but instead they show the API min spec HTHS for that viscosity.


As far as I'm concerned, "No HTHS numbers, no purchase."

 

[Jetronic]

Originally Posted By: splineman
I still find it interesting that viscosity # is not the whole story and the 15-40 is apparently more robust in service but thinner at startup than a 15w-50.
A friend uses shell hx3 20w-50 in his bike and its very reasonably priced but no hths figures I can find so have avoided it.
Castrol may not be what they were but they aren't shy to charge.


I'd ask Joe90_Guy about the Shell if I was you.