Yes they do. As in helping to ensure an adequate film thickness. But you have to add mechanical devices and complexity to do that with low HT/HS oils.
KIA Turbo oil
- Thread starter BMWGUY2
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Most Korean engines have very high oil temperatures, 270F is not uncommon in the summer.
For thicker oil. Everyone knows that modern engines are designed with much tighter tolerances and thats partly why they need thinner oil. Reduced emissions and improved fuel economy and other reasons for it but the notion that thicker oil is always better is the old way of thinking.
Really?
”Much tighter tolerances”?
Tighter than what engines, what vintage, exactly?
If this were true, that tighter tolerances are a characteristic of “modern” engines, then how could Toyota, or any other manufacturer “back-specify” a thinner viscosity on older engines?
They aren’t modern, and therefore must have looser tolerances, right?
So, they clearly can’t handle a lower viscosity, because of the lack of those ”much tighter tolerances” in older engines.
And yet, whose older, looser engines are getting updated, lower viscosity, oil specifications.
Which couldn’t work, unless…those old engines had the same tolerances…
How do you explain engines used in other countries without CAFE type mandates specifying a whole range of oil viscosity? Or motorcycles (no CAFE) that also specify a whole range of viscosity? If you look at the journal bearing and piston to cylinder wall clearances on a new car/truck/motorcycle to ones built 35 years ago the clearances are not really tighter now.
Just think how thick 0W or 5W oil is at tempatures below zero. If engine clearances in newer engines were "so much tighter" and needed much thinner oil to lubricate them, then why aren't they being damaged or blowing-up in the winter climates? 0W-xx at below zero is 100s of times thicker than xW-50 at 200F. Yet engines don't become damaged from running on that relatively very thick cold oil.
The mantra that "engines with tighter clearances need thinner oil" for proper lubrication is a misconception that somehow got traction through people trying to justify using CAFE driven low viscosity oil.
Jackson_Slugger
$50 Site Donor 2022
I severally doubt this...
It may have an oil cooler but going well into the 200F's isn't a problem for a good syn 0W-20, personally I would snap if the oil temp only got to 180F as the real issue is moisture rotting the oil in cold starts over time and turning it acidic...
Like the fools here that autostart their cars in winter a half hour before driving, because god forbid they have a cold fanny or experience any discomfort whatsoever, are actually doing a lot more damage to their engines than driving on a highway in a 90F+ day with a 0W-20...
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Jackson_Slugger
$50 Site Donor 2022
I'm not a "thicker oil" guy but I think it is a vast overgeneralization to say that "tolerances are tighter". I think more so that today's engineering and machining are much more precise and that is more the factor, which is why we really don't need the 500 mile initial OCI dump on today's new cars. Materials used in engines are superior today and can handle using "thinner oils" (which we've always used, and today's oils are vastly superior to the waxy Group I bases of yesterday and 5W-20 wasn't invented in 1997, it was a standard GM winter weight in the mid-60's and SAE20 was often used in commercial trucking in moderate temps. so "thinner oils" in appropriate applications is nothing new). The reduced emissions is largely due to better additive packages, better gas, and the reduced use of zinc...
Jackson_Slugger
$50 Site Donor 2022
Jackson_Slugger
$50 Site Donor 2022
Indeed, Kia's/Total's "Turbo Oil" is a bit intriguing, I wonder what the dealership gets for a quart...
I believe it's made by Shell / SK to Mobis specifications.
It's not distributed to most markets though sadly.
My Genesis Coupe 2L turbo came from the factory with 5w20. They quickly changed that to 5w30 minimum with a TSB. I usually ran 0w40. Been on 5w30 for the last two changes. Going back to 0w40 though due to fuel dilution. I do go 5k mile OCI.Daughters 2020 KIA Soul 1.6T calls for 5w30 on the cap.
The oil temp usually runs 10F over coolant temp in the summer. In winter near the coolant temp. 183F-187F
Everyone knows?
You might tell that to Toyota, BMW, Mercedes, Honda etc.
They apparently don’t know it.
OVERKILL
$100 Site Donor 2021
Tolerances or clearances?
Manufacturing techniques have improved markedly, generally, over the past century. This led to a lot of automation and, in recent decades, "bulk" fitting of things like pistons, which, in turn, led to issues with perhaps insufficiently tight tolerances in piston-to-wall clearance, which, in some instances, was too wide, and, as a result, when combined with short skirts to reduce friction, we got piston slap. Not an issue with the hand fit stuff built during the 80's.
Clearances, have generally remained unchanged. If you look up OE bearing clearances for a 1960's vintage Ford Windsor, you'll find it remarkably similar to what we see spec'd for more modern mills that dictate much thinner oils.
We've also seen widespread adoption of special coatings and surface finishes, but that's a separate discussion.
The one area we have seen change is with bearing width in engines that are designed around oils with an HTHS of well below 2.6cP. One of the Honda papers, from which excerpts have been shared on here many times, in their remarks about "acceptable" wear, noted that bearing width had to be increased to allow for the thinner oil film to perform adequately.
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I just love the way you do this. Then they have nothing to withstand your knowledge and understanding. You've taught me a good bit on these forums. Thank you.
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