Trying to understand SUS & cSt viscosity

[SJohnson]

So here's what I don't understand. I recently did a UOA. Oil was regular MaxLife 20W-50. The oil was used in my Harley. Everything looked good except the SUS & cSt were slightly out of spec. SUS was 81.6, S/B 82-95. cSt was 15.93, S/B 16.0-19.4. So both were barely out of grade on the low side. Here's the report:

http://www.bobistheoilguy.com/forums/ubb...248#Post3629266

So, I started looking around at other 20W-50 UOA's and VOA's and noticed the SUS & cSt ranges were different depending on the manufacturer. Here's one for VR-1 and another for Syn 3 that shows a SUS range of 77-94 and a cSt of 14.8-19.2.

http://www.bobistheoilguy.com/forums/ubb..._HD#Post1967684

http://www.bobistheoilguy.com/forums/ubb..._49#Post3662849

Here's one for VOA of the same Syn 3 oil that shows SUS of 81-102 and cSt of 15.8-21.1.

http://www.bobistheoilguy.com/forums/ubb...gle#Post3652062

And finally, here's some Redline that shows SUS of 86-102 and cSt of 17.0-21.1.

http://www.bobistheoilguy.com/forums/ubb...n_a#Post3394549

So why are the SUS and cSt different for the same "weight" oils? Why are the Syn 3 VOA and UOA different? How much of a concern is it that the MaxLife was slightly lower that it should be? If it was Syn 3 or VR-1, it would still be in spec. I've done a lot of searching and I can't find the answer and it doesn't make sense to me. I'm sure someone here knows the answer and can explain it to me.

Thanks in advance.

 

[Rand]

20w50 is a viscosity range

Sus and cst are directly comparable. measuring the same property

(like meters and feet)

IIRC 20w50 should be above 16.3 and less than 21.9

 

[mjoekingz28]

Im still learning, but i dont think it is weight you are looking at, it is grade.


Can someone back me up or correct me?

 

[SJohnson]

Originally Posted By: mjoekingz28
Im still learning, but i dont think it is weight you are looking at, it is grade.


Can someone back me up or correct me?


It may be grade, that's why I put "weight" in quotes. Either way, it doesn't look like anyone here knows the answer, of which I'm kind of surprised. I felt sure that at least one person would know the answer.

 

[OVERKILL]

Originally Posted By: SJohnson
Originally Posted By: mjoekingz28
Im still learning, but i dont think it is weight you are looking at, it is grade.


Can someone back me up or correct me?


It may be grade, that's why I put "weight" in quotes. Either way, it doesn't look like anyone here knows the answer, of which I'm kind of surprised. I felt sure that at least one person would know the answer.


Rand answered your question.

 

[SJohnson]

Originally Posted By: OVERKILL
Originally Posted By: SJohnson
Originally Posted By: mjoekingz28
Im still learning, but i dont think it is weight you are looking at, it is grade.


Can someone back me up or correct me?


It may be grade, that's why I put "weight" in quotes. Either way, it doesn't look like anyone here knows the answer, of which I'm kind of surprised. I felt sure that at least one person would know the answer.


Rand answered your question.


Then why does this UOA show a range of: 14.8-19.2?

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3662849/1

 

[Quattro Pete]

Originally Posted By: SJohnson
Then why does this UOA show a range of: 14.8-19.2?

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3662849/1

That is just what Blackstone Labs thinks is the expected viscosity range of a USED 20w-50 oil. It is very subjective and I still don't fully understand why they come up with their own ranges.

As far as SUS and cSt, they are directly comparable. They just use different units of measure.

 

[OVERKILL]

Originally Posted By: SJohnson
Originally Posted By: OVERKILL
Originally Posted By: SJohnson
Originally Posted By: mjoekingz28
Im still learning, but i dont think it is weight you are looking at, it is grade.


Can someone back me up or correct me?


It may be grade, that's why I put "weight" in quotes. Either way, it doesn't look like anyone here knows the answer, of which I'm kind of surprised. I felt sure that at least one person would know the answer.


Rand answered your question.


Then why does this UOA show a range of: 14.8-19.2?

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3662849/1


The range for a 50-weight is shown here:

16.3 to 21.9 cSt.

The range shown by Blackstone is simply what they deem "typical" and doesn't actually reflect the actual range for a given grade. It is what they have seen as the "normal" range for that grade.

Make sense?

 

[dustyroads]

Blackstone is very responsive (in both willingness and speed) to emails. If you use their website to drop a line and include your client ID they will gladly clarify for you. They can be specific using your report and address the other samples you mentioned.

It's one of the reasons I use them.

 

[SJohnson]

Originally Posted By: Quattro Pete
Originally Posted By: SJohnson
Then why does this UOA show a range of: 14.8-19.2?

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3662849/1

That is just what Blackstone Labs thinks is the expected viscosity range of a USED 20w-50 oil. It is very subjective and I still don't fully understand why they come up with their own ranges.

As far as SUS and cSt, they are directly comparable. They just use different units of measure.

Thanks. That's what I was looking for.

 

[SJohnson]

Thanks OVERKILL. Makes sense now.

 

[OVERKILL]

No problem

 

[SJohnson]

Originally Posted By: dustyroads
Blackstone is very responsive (in both willingness and speed) to emails. If you use their website to drop a line and include your client ID they will gladly clarify for you. They can be specific using your report and address the other samples you mentioned.

It's one of the reasons I use them.



Thanks. I may try that.