Is 10w40 shearing a thing of the past?

[The motor guy]

Is something like a 5w40 or 10w40 shearing down to a straight 5 or 10 weight a thing of the past? Or will this still happen in high heat situations? Like in a lawn mower?

 

[FCD]

A few years ago SAE J300 was revised and the minimum HTHS was raised from 2.9 to 3.5 for 0W,5W and 10W-40 oils , 15w40, 20W-40, 25W-40 and Straight 40 have minimum of 3.7
This has helped certainly and 10W-40s no longer shear anywhere near as much as they used to.
For a lawn mower i would rather run a cheap 15w40 HDEO , since they are far more "robust" compared to a run of the mill 10W-40 PCMO.

 

[Popsy]

From my -limited- experience with 5W40 and 10W40 oil in my old diesel (oil cooled turbo, fuel dilution, small sump = less than ideal conditions), pcmo 10W40 don't resist as well as good quality 5W40, and obviously 15W40 oils. That's only my opinion over the limited oils I've tried, mainly big brands entry levels 10W40.

Now HDEO 10W40 like Shell Rimula was another thing, and I have currently good results with some Total 10W50.

 

[AirgunSavant]

I picked up some Delo 400 SD SAE 15w30 on sale at Amazon for $13 a jug.
This coming year I'm going to run it in a zero turn. I have a bunch of property to do and I want to see
how it works out.

 

[CT8]

Originally Posted By: motor_oil_madman
Is something like a 5w40 or 10w40 shearing down to a straight 5 or 10 weight a thing of the past? Or will this still happen in high heat situations? Like in a lawn mower?
They never sheared to a 5 or 10 [they did shear] but the problem was the Viscosity Improvers would cause the rings to stick and cause oil burning.

 

[BrocLuno]

Originally Posted By: AirgunSavant
I picked up some Delo 400 SD SAE 15w30 on sale at Amazon for $13 a jug.
This coming year I'm going to run it in a zero turn. I have a bunch of property to do and I want to see how it works out.


My bet is it's going to be a real good run

I got my stash of 15w30 for fresh engine break-in... Got a few to build over the next few years

 

[Nickdfresh]

Originally Posted By: motor_oil_madman
Is something like a 5w40 or 10w40 shearing down to a straight 5 or 10 weight a thing of the past? Or will this still happen in high heat situations? Like in a lawn mower?


You can always do a survey of UOA's here. I suspect that they don't shear as much as they once did say 15-20 years ago...

 

[BrocLuno]

The 5W's will have a pretty good slug of at least Group III, so they are less susceptible. Cheap 10W's could still be Group I with a ton of VII's so that could be iffy... But it would not likely be a product from one of the majors ...

It's all about the blend

 

[UltrafanUK]

You are more likely to get an 0w40 shear down than a 10w40 IF they used the same base stock. The bigger the difference between the 2 SAE groups, the more viscosity improvers are required. Anything more than a 40 spread for an engine oil tends to make it more of an issue.

 

[BrocLuno]

The problem here is the shelves have oil that are not even close to the "same base stock"... There will be some inexpensive 10W-40's out there still made out of Grp I

 

[FCD]

You would have to try your best to find a Group 1 conventional 10W-40 in Europe, 99% of them are semi-synthetics.

 

[Jetronic]

Never found one either. All are semi-synth here, but the 15w40 and 20w-50 are mineral and most likely group I

 

[SR5]

According to this presentation from Joe,
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4261586/

Most of your European 10W-40 semi-synthetics would contain a decent amount of Group 1 oil.

 

[jongies3]

I run straight 30wt in my mower, just the O'Reilly's brand stuff, nothing fancy. Mowers don't really need a multigrade oil since they're typically ran in the summer and rev high with low airflow.