5W-30 Shear question

Gary Allan · Jan 28, 2010

Johnny · Jan 28, 2010

Darn Gary, you working overtime?

ThirdeYe · Jan 28, 2010

Here's another UOA you can use as reference that 5W-30's don't always sheer:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1486954

Brian Barnhart · Jan 28, 2010

14 links. One duplicate. 2 blends. That leaves 11 samples of 7 different 5W30 dino oils. And of those 10 samples, four had additional oil additives. That would leave 7 samples of 5 different oils staying within grade. How does that show a particular 5W30 dino does not routinely shear?

Yesterday, I looked at all the examples of the dino 5W30 UOAs on the first page at the time (5 samples), and every one sheared to 20W. Not exhaustive, but at least somewhat random. When I looked more closely at 5W30 oils about 2 years ago, I found:

8 of 10 dinos sheared to 20W, with an average 100C cSt of 8.77 (six different oils represented).

1 of 10 synthetics sheared to 20W, with an average 100C cSt of 10.5 (three different oils represented).

To support the statement that a particular oil doesn’t routinely shear, I would want to list a representative number of samples of that oil, a majority of which show the oil didn’t shear.

Cherry picking examples of all dino 5W30 samples that didn’t shear isn’t conclusive.

I will say that from all the samples of dino 5W30 I’ve seen, there is one brand that may not routinely shear in many non-turbo applications. But I don’t have enough data to be fully convinced.

I’ll also add that staying in grade isn’t an end-all benchmark for oil protection in every engine.

Gary Allan · Jan 28, 2010

Well, here's where I think you're missing my point on the UOA's. Many of those same engines ALSO routinely degrade 5w-20 to the SAME 1.X+ cSt level. That is, it's not the 5w-30 conventional shearing (most are around 10.5 cSt so it's only 1.3cSt to sub 30).

That is, NO ONE ever calls a 5w-20 ..that's a virtual 5w-30 minus 1.x tick into 20 range virgin as "shear prone" when the UOA reads in the 7.xcSt ..they attribute it to the engine family characteristic. The 5w-20 may slide 15% of it's virgin visc and it's invisible. The 5w-30 may slide
Yet a 5w-30 that starts @ 10.5cSt that hits 9.20 is shearing due to its characteristics.

The difference you can see with all the mass usage of conventional 5w-20 is that some engines shear it ..and some do not.

Brian Barnhart · Jan 29, 2010

It appears many energy conserving GF-4 dino oils shear in real world use.

However, when the viscosity of an xW20 drops from 9.x to 7.x cSt @100 C it’s still within the 20W SAE grade. (The 20W min cSt @100C is 5.6). So by definition the 20W didn’t shear out of grade.

What I find interesting is that while dino 5W30s often shear out of grade when used in many engines, those same oils do not by definition shear out of grade in the Sequence VIII test. So it could be argued that the test doesn’t replicate the shearing that occurs in many engines in real world use. The up side is that the longevity of 5W30 spec’d engines does not appear to be compromised by oils that shear to high 20W.

Gary Allan · Jan 29, 2010

Quote:
However, when the viscosity of an xW20 drops from 9.x to 7.x cSt @100 C it’s still within the 20W SAE grade. (The 20W min cSt @100C is 5.6). So by definition the 20W didn’t shear out of grade.

You're not serious. I can't see you seeing that as some standard of viability. For a 20 weight to shear out of grade it would have to drop nearly 40%+/- in viscosity to
In any event, when seeing a "shear prone" 5w-30 ..try and look up the same engine using a 5w-20 (sometimes even a synthetic) to see if it's also "shear prone". At that point you can figure that it's not the oil as much as it is the application. Many engines beat the tar out of any oil ..but don't seem to show any regard to visc ..or lack of it.

Johnny · Jan 29, 2010

The shearing of a well formulated oil does not bother me. It's when it starts to re-thicken back up in a hurry that bothers me.

Brian Barnhart · Jan 29, 2010

Gary,

If you don’t like the dividing lines or spreads of the SAE grades, or don’t believe they are good guidelines, perhaps you should enlighten the SAE with your subjective views.

I’m working with the definitions and data I can find.

The OP question was: “Is it true that most dino 5W-30 oils shear to 20wt after little use?” When looking at SAE definitions and representative UOA data posted here, I believe the best objective yes or no answer is yes.

Trying to argue that it’s not necessarily a problem if a 5W30 becomes a 5W20 with use isn’t a proper answer to the original question.

Gary Allan · Jan 29, 2010

Quote:
Trying to argue that it’s not necessarily a problem if a 5W30 becomes a 5W20 with use isn’t a proper answer to the original question.

Get a quote where I said that?

I merely said that your assertion that 5w-30 routinely sheared was perhaps in error. I then showed a few (which if you noticed DID NOT PROVE MY point) where they stayed in grade. I suggested that before you assume that all 5w-30's are shear prone due to the appearance of shearing that you compare it to the same engine(s) where a 5w-20 has been used and see how you "all of a sudden" lose the "it's shear prone" view. You'll then automatically assume "it's the engine". Then go back and rethink your life choices and put down the death sticks (waves hand)

NightRiderQ45 · Jan 29, 2010

thanks for all the replies fellas. I wanted to use MC 5w-20, which I thought would be ok but I might just stick with 5w-30. There are so many people who run a different grade than what's on their dipstick so I honestly don't think my engine will know the difference between the 5w-30 or 20wt. I know that some people said to take "caution"...could anyone explain why I should be?

Gary Allan · Jan 29, 2010

Use either in confidence and in good health!

Brian Barnhart · Jan 29, 2010

Originally Posted By: Gary Allan
Quote:
Trying to argue that it’s not necessarily a problem if a 5W30 becomes a 5W20 with use isn’t a proper answer to the original question.

Get a quote where I said that?

I guess I read too much into your statements about what 5W20s do when the question was about whether a 5W30 shears to a 20W in use. That and "Many engines beat the tar out of any oil ..but don't seem to show any regard to visc ..or lack of it."

5W-30 Shear question

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