And THAT gets to the crux of the answer.
Will Thinner Oils Damage Your Engine?
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I'd say there are some pretty high HP/CI engines (with good oil coolers) out there that spec xW-20 for CAFE purposes. And some manufactures (where CAFE dosn't exist) spec or at least say that it's fine to run thicker oil than xW-20 in low performance engines.
that's why I come here, entertainment and self established experts 
Extreme cold is one of the reasons why synthetic lubricants originated (the others were extreme heat and lack of crude oil).
Manufacturers of synthetics like Emery Industries' diesters (which became Hatco) formulated motor oils - in Emery's case "Frigid Go" - that would flow in extreme low temperatures since they lacked paraffins and could be more readily tailored.
The Big Debate Over Synthetic Oils For Your Car
They also took some of the load off batteries when starting and provided better lubrication to engine bearings while the engine warmed up.
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Agree! Bottom line, if your vehicle is spec'd for xW20, use a good quality synthetic xW20 and don't worry about engine damage. It's been nearly 20 years since 5W20 was introduced. Probably going to take another 20 years for old folks (or they will be dead by then) to accept that a full synthetic xW20 will not damage your engine if it is spec'd to run xW20. I reiterate FULL SYNTHETIC. Not that BS synthetic blend.
NASCAR engines run lower than 0W20 viscosity oils.
There's a difference between "damage" and more long term wear. But if an engine was pushed extremely hard for a long period of time with too thin oil due to extremely elevated oil temperature it certainly could get "damaged". That's why I like a little more MOFT headroom than not by bumping up the viscosity (ie, xW-20 to xW-30).
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5W20 conventional will provide the same protection if it meets the specifications of the engine.
Also, 5W20 has been out a lot longer than nearly 20 years.
They do not plan on keeping the engines until next year's models come out.
Those oils have:
- extremely high additive levels
- little or no detergents
- are dumped after every race
Neither those oils nor their use are relevant to the discussion, which is about ordinary folks driving ordinary cars with the new thinner oils.
https://www.enginelabs.com/tech-stories/racing-oil-vs-street-oil-know-the-differences/
And what's the maximum miles they drive on that engine. 500 miles? But if a manufacturer mainly, Toyota and Honda, properly designed an high performance engine to run on 0W20. I'll run 0W20
Unless you tow a trailer, drive in extreme heat, beat the engine, drive at very high speeds, in which case you may want to up it to an XW-30 or even an XW-40.
I believe it is relevant to his post, because HP engines can survive on 0W oils for hundreds of miles at high RPM's. In regard to ordinary folks driving ordinary cars, a new 2020 Mustang GT specifies 5W20.
I really don't need your teaching on street vs strip oil. I build, race, and drive many vehicles both on and off road. Please let me know if you have any questions on those topics and I'd be happy to help you.
I really don't need your teaching on street vs strip oil. I build, race, and drive many vehicles both on and off road. Please let me know if you have any questions on those topics and I'd be happy to help you.
I have a Toyota Tundra that calls for 0W20. I live in South Texas and and do a lot of towing. UOAs showed no issues. This truck has an 8.5 oil sump and an oil cooler. Do not see a reason to go to xW30 or xW40. To each their own. It's your vehicle and your $$$$$. Do what helps you sleep at night but running 0W20 will not damage your engine.
I've towed across the country on 5W20 conventional, with a max load, at 80 MPH, up the Ike Gauntlet, with NO engine damage.
Interesting, do you know which engines?
I think i posted in another thread (or maybe this one) that Ford Australia updated the owners manual (3rd revision) for the 2015 Mustang to change the 5.0 oil from 5w20 to 5w30. I wonder if this was in response to what you mentioned, or if it was exactly what you mentioned.
Is this quantifiable? (no damage part) or based on UAO?
Also, another question, i know for Blackstone at least, their UOA "is it good or is it bad" is basically based on their past results, the history and averages of previous oil tests - my thoughts there being, is it possible that if everyone running (for arguments sake) 5w20 on an engine that specifies it, the UOA's will all show "OK" because everyone's wear averages will be similar.
"survive on 0W oils" is a bit off since that's the cold rating, so it depends more on the hot viscosity.
From the 2018+ Owner's Manual about track use. Sure, xW-20 is OK for relatively benign use (still may result in more long term wear), but higher viscosity is needed/recommended for increased MOFT when the engine is pushed hard - for obvious reasons.
That may have been the 4.0L V6 and perhaps earlier OHV 3.0L's?
I'd be surprised if Ford recommended 5W30 for any 5.0L Coyote, especially one year only. I find that modern Mustangs and F series control oil temps very well! Please let us know if you find a document on that.
I didn't check other years, i check the first year for the "international Mustang" and thus the same 5.0 engine in my F150 (albeit tuned differently) and it's in Ford's own downloadable owners manual, there are 3 revisions on Ford Australia's website and in the 3rd revision, the 5.0 oil spec changed from 5w20 in the first two revisions, to a 5w30 specification in the current/3rd revision.
For what it's worth, there were pretty reasonable changes to the 5.0 in 2018, so not a good comparison for following years.
All 2015+ Mustangs with the Coyote sold in Australia specify 5W-30.
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