Some questions about 30wt oils

Shel_B

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One of the things I read on BITOG is that some folks prefer a 10W-30 to a 5W-30 oil because it has a higher HT/HS and provides greater protection. However, I've noticed that many 5W-30 oils have a higher viscosity and, from what I've read here, that would equate to a greater HT/HS. Since I'm a Mobil1 user, I'm most familiar with their specs, although I've seen similar numbers with other brands. For example, here are the numbers for M1 EP:

Capture2.JPG


So what, if anything, makes the 10W-30 a more desirable or stronger oil than the 5W-30? Might it be that the 10W has less or different viscosity improvers? Would this 5W have a greater HT/HS than the 10W?
 
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blupupher

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I think that most will say the reduced amount of VI is their reasoning.

For me, I really have no need for cold weather starting oils.
This year was one of the coldest winters we have had and even that was only 14°F for a low, and the area was shut down anyway due to ice on the roads, so vehicles not going anywhere anyway.

I could probably get away with straight SAE 30 oil.
 
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Shel_B

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I think that most will say the reduced amount of VI is their reasoning.
Aren't there different types and qualities of VIs? Do we know, for example, if the VI in a 5W-30 oil is similar to that in a 10W-30 oil? Could it not be stronger, less prone to shear, more durable under difficult operating conditions? Is there a type of VI of which less is needed to get a similar result?
 

blupupher

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I thing is, most (including me) don't truly understand the depth that VI play, and how each manufacturer uses different formulations to get the results they want.
Is one oil brand "better" than another? Maybe.
Is the difference something that can be measured? Possibly.
Is it enough to make a real world difference? No idea, but in my non-professional and non-expert opinion, not enough to make any real difference for most.

A lot of this feeling also goes back 20 years when dino oil was king and oil quality was much lower than now days.
With modern oils being at least some type of a syn blend, I don't think it plays as much a role as it used to.

For me personally, I don't worry about it that much.
I am using 10w-30 in my '18 Santa Fe.
Why, because I have a bunch I got for cheap and it is a spec'ed oil for that vehicle in my climate.
I also have no qualms using 10w-30 in most any engine, and have done in a few in my fleet in my sig.
Again, my climate is what 10w-30 is designed for.
 
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One of the things I read on BITOG is that some folks prefer a 10W-30 to a 5W-30 oil because it has a higher HT/HS and provides greater protection. However, I've noticed that many 5W-30 oils have a higher viscosity and, from what I've read here, that would equate to a greater HT/HS. Since I'm a Mobil1 user, I'm most familiar with their specs, although I've seen similar numbers with other brands. For example, here are the numbers for M1 EP:

View attachment 76358

So what, if anything, makes the 10W-30 a more desirable or stronger oil than the 5W-30? Might it be that the 10W has less or different viscosity improvers? Would this 5W have a greater HT/HS than the 10W?

It has nothing to with HTHS but cost. The viscosity range of a 30w is 9.3 cSt to 12.5 cSt so iirc the HTHS will differ so just buying a SAE30 doesn't guarantee you'll have the highest HTHS.

For example take a look a the HTHS of the 30w PCMOs from a forum sponser - https://www.hplubricants.com/wp-content/uploads/2021/08/PC-Engine-Oil-PDS.pdf
 
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A lot of folks don't have any grasp of variance within a given oil grade. They don't know what you stated or often don't realize some 5W's are thicker than some 10W's at operating temp or vice versa. These folks know "just enough to sound stupid". You can usually tell by the overconfident attitude. 😁
 
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I can also use a 10w30 year round in my climate. Due to a noisy lifter, I often used 10w30 in my C4 Corvette (spec'd for 5w30) and the 10w quieted that lifter, mostly. I was also under the impression that 10w30 is generally a bit more "robust" than 5w30, but this is not necessarily true. 5w30 is such an extremely common spec that most brands of finished lubricant have probably put a lot of research into their 5w30 formulation. Maybe this is an assumption but it makes sense inside my brain.
 

ZeeOSix

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If you're concerned about HTHS, then pick a viscosity that gives you the HTHS you want, while picking an appropriate "W" rating for your climate.
 
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I can also use a 10w30 year round in my climate. Due to a noisy lifter, I often used 10w30 in my C4 Corvette (spec'd for 5w30) and the 10w quieted that lifter, mostly. I was also under the impression that 10w30 is generally a bit more "robust" than 5w30, but this is not necessarily true. 5w30 is such an extremely common spec that most brands of finished lubricant have probably put a lot of research into their 5w30 formulation. Maybe this is an assumption but it makes sense inside my brain.
Heck, most all the marketing claims have a fine print disclaimer stating the results or claims apply to 5w30, so you're probably right.

In the modern age of synthetic oil there is no good reason to use an ILSAC 10w30 over a 5w30. If you want an extremely stable oil that won't lose kinematic or HTHS viscosity then a 15w40 or 10w30 multi fleet HDEO oil is the way to go.
 
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SR5

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One of the things I read on BITOG is that some folks prefer a 10W-30 to a 5W-30 oil because it has a higher HT/HS and provides greater protection. However, I've noticed that many 5W-30 oils have a higher viscosity and, from what I've read here, that would equate to a greater HT/HS. Since I'm a Mobil1 user, I'm most familiar with their specs, although I've seen similar numbers with other brands. For example, here are the numbers for M1 EP:

View attachment 76358

So what, if anything, makes the 10W-30 a more desirable or stronger oil than the 5W-30? Might it be that the 10W has less or different viscosity improvers? Would this 5W have a greater HT/HS than the 10W?
Just to be clear, I assume that table shows (top to bottom) grade, flash point (deg C) and KV100 (cSt).

None of which are the actual HTHS value (cP). That general assumption is that the higher the KV100 will have a higher HTHS. But you have shear to deal with, both temporary and permanent.

It would be interesting to see the KV100 (and HTHS) value after something like 5k miles. Then you may find the situation has reversed and that the 10W30 is now the thicker (KV100) oil, as it should suffer less shear. But hard to tell without before and after data.
 
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SR5

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Aren't there different types and qualities of VIs? Do we know, for example, if the VI in a 5W-30 oil is similar to that in a 10W-30 oil? Could it not be stronger, less prone to shear, more durable under difficult operating conditions? Is there a type of VI of which less is needed to get a similar result?
I'm no VII (viscosity index improver) expert, but in general I believe that you are trading off three properties: expense, shear stability and efficiency. For the same cost & chemistry, a more shear stable VII is less efficient (meaning you need more to do the same job).

I also believe that more VIIs in an oil tend to create more deposits. So a more shear stable 5W30 often means more VII and the risk of more deposits, unless you run a more expensive VII chemistry. However a 10W30 requires less VII to begin with, and so more options are open to you in terms of shear stability and deposit control. However a 10Wx oil is only rated down to 0F (-20C) which mean it's not suitable for very cold climates.

My general rule of thumb is "as much cold starting as you require, but no more than you require". In my climate I can use a 10W30 or 15W40, year round. The reality is, I am running a synthetic 5W30 in both cars, why? Because the 5W30's were on sale, and a good BITOGer likes a good oil sale.
 

OVERKILL

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Aren't there different types and qualities of VIs? Do we know, for example, if the VI in a 5W-30 oil is similar to that in a 10W-30 oil? Could it not be stronger, less prone to shear, more durable under difficult operating conditions? Is there a type of VI of which less is needed to get a similar result?

While pointing out that SDS sheets aren't recipes, unless we are talking about oils already blended "on the cheap", the base oil composition will be different:
Screen Shot 2021-11-04 at 10.09.58 AM.png

Screen Shot 2021-11-04 at 10.10.16 AM.png


Note the concentration of PAO and how it changes between the two oils. Using PAO means less VII, because you can improve the cold temp performance and manipulate viscosity by using the naturally higher VI base oils.

I'm sure you recall these:

Screen Shot 2020-09-08 at 9.02.43 AM.png

Screen Shot 2020-09-08 at 9.20.49 PM.png


While not similar formulations (the 10w-30 is an HDEO, so HTHS is higher) the 10w-30 is blended using straight Group II+, while the 5w-30 still has Group III in it.
 
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Shel_B

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Quite helpful, Overkill. This is what I'm trying to understand. Thanks for some useful information.
 
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