10w30 thinner than 5w30?

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I have been noticing that when i look at many specs for oils that the 10w30 is slightly thinner than there corresponding 5w30s. This appears to be true for formula shell, M1 and others. Does anyone know why this is?
 
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Assuming we're talking "hot" viscosity, yes, that can be true. As noted above, it's all up to the chemical engineers who design the fluids. A prime example are the 30 wt Mobil-1 products. In the "regular flavor" M1, the 5w-30 grade is 11.3 cSt at 100 deg, whereas the 10w-30 is substantially thinner at 10.0 cSt. Don't be confused by the "w" part of an oil's rating, which of course, speaks only to the oil's behavior when it's cold. Given today's technology, it's no stretch at all, obviously, for a 10w-30 to be thinner at high temps than even a 0w-30 (think GC as a prime example).
 
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 Originally Posted By: bepperb
A 5w30 is more suceptible to thinning, so I wouldn't be surprised they would start them a bit thicker.
Not necessarily true at all. If it's a lower quality product (the existence of which is debatable under the SM standards) that contains "lesser" VIIs, then maybe a particular 5w-30 is more susceptible to shearing down (as opposed to just thinning). But otherwise, a 5w-30 is absolutely NOT any more likely to "thin" than either a 0w-30, a 10w-30, or even a straight SAE-30 oil. How a given fluid behaves as its temperature increases is a function of the quality of the product, and the targets its designers were shooting for. You absolutely cannot, with any validity, make such broad generalizations about modern oils.
 
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"You absolutely cannot, with any validity, make such broad generalizations about modern oils." Well, it's one theory, and while not necessarily true about every oil, it's not as off the wall as you make it seem. Maybe we can agree that if we were talking about non-detergent conventional oil from the 70's it would be true. But things have come a long way since then. You make a good example of M1 5w30 being thicker than 10w-30 at boiling. I'd love to hear your theory of why this is...
 
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 Originally Posted By: bepperb
. . . You make a good example of M1 5w30 being thicker than 10w-30 at boiling. I'd love to hear your theory of why this is...
It's very simple actually, no theory necessary, see the charts, below. First off, the SAE ratings are NOT absolute points on the viscosity/thickness scale. Any oil that when hot is between about 9 cSt and 12 cSt counts as a "30 wt" oil. No mystery there. Second, I think you're making a commonly seen error -- mistakenly believing that hot viscosity is related to the cold "w" rating -- they're really not. The product that's an old favorite here, GC (German Castrol), comes only in 0w-30, and is in fact thicker than most all other 30s, irrespective of grade. It gets the 0w rating not for "thinness", but rather for its exceptional ability to remain liquid and pumpable at temps that would leave a lower-quality 5w-30 a solid lump of goo. Finally, given the wide range of quality additives available today, and of course, high quality base oils, it's child's play for an oil formulator to make a 10w-30 that's much thinner when hot than another 5w-30. Did you overlook the Mobil-1 example I gave earlier? So, if you won't take my word for it (and that's OK), here's some hard evidence -- annotated screen captures taken from the Mobil website today. As you can plainly see the Mobil-1 5w-30 is significantly thicker than the Mobil-1 10w-30. Any questions???
 
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And another thought. Looking at the two common flavors of normal M1, notice how the 10w-30 is actually thinner both when hot, AND when cold. But despite it being "thicker" when hot, the 5w-30 has a notably lower HTHS viscosity than does the 10w-30. I wonder if this particular 10w-30 might also be legitimately labeled as a 5w-30 too? A tad OT, but these charts do seem to raise some tantalizing questions.
 
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 Originally Posted By: Pablo
pwned. OK OK Reasonably well written! ;\)
Muah-ha-ha-ha! Seriously though, I just noticed that I inadvertently chopped the pour point off the screen capture of the 10w-30 specs. It's -45C, only three degrees higher than the 5w-30. For me, this begs the question of why, particularly in a climate like mine, anyone would bother with the 5w-30 instead of the 10w-30?
 

jstutz

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 Originally Posted By: ekpolk
 Originally Posted By: Pablo
pwned. OK OK Reasonably well written! ;\)
For me, this begs the question of why, particularly in a climate like mine, anyone would bother with the 5w-30 instead of the 10w-30?
maybe becuase the 5w30 is a little thicker when hot. Then agian 10w30 has a little HTHS. Looks to me you could toss a coin and make about as good of a judgement call. I understand how they could make a 10w30 thinner when hot then a 5w30 i just dont understand why they would. maybe they dont need as many VII as 5w30 so they dont sheer as fast so they can get away with making it a little thinner to start with. That is just a guess. I have usually been running 10w30 in my stuff in the summer and now im not so sure there is really a reason too. So if you wanted to look for a litte added protection say for an old truck, should you look at the viscosity at 100C or at the HTHS to gauge which is better?
 

jstutz

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 Originally Posted By: ARCOgraphite
I not so sure PP is as good an indicator of cold performance as CCS/ MRv #s? Oui?
What?
 
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 Originally Posted By: ARCOgraphite
I not so sure PP is as good an indicator of cold performance as CCS/ MRv #s? Oui?
I absolutely agree. I was just pointing out, though inartfully, that in some respects, the two oils are quite similar. I would say, however, that pour point remains lurking prominently in the background. Obviously, if your oil has gone solid (or nearly so), it isn't going to pump real well. Of course, where I live, I worry about my Sega palms getting a wee bit of frostbite on a +20-something morning, so I'm not exactly "well schooled" in when such things become truly critical. EDIT: btw, I briefly saw triple digits (101F) on the Camry's outside air temp display yesterday, and 99F today. I'm more concerned about this end of the temp scale.
 
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Epolk, I do enjoy the discussion. I guess what I don't understand, and what still hasn't been touched upon, is why does Mobil make 0w-30, 5w-30, 10w-30 and SAE30 if there was no reason not to just use the 0w-30. Keeping it just to 5w-30 and 10w-30, it does seem like they are very similar and could be combined into one product with a label simply stating "for all 5w-30 and 10w-30 applications". Is it for people worried about warranties? Is it like toothpaste, where the more products we have the more shelf space we get, so the more the merrier. Maybe it's a bit childish, but I want to know WHY! What advantage does a SAE 30 have over a 0w-30 anymore, if not for resistance to shear. And generalizations are ok with me. Tantalizing questions? The entire forum is a black hole of tantalizing quesitons with no answer. So why M1 10w-30 is thinner than 5w-30 at both temps is perfect for this place...
 
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