Dealership added the wrong oil

I think your assumption that all oils are the same viscosity once the engine reaches operating temperature is probably wrong.

 

Do I really need to spell this out?
First, I never said that ALL oils are the same. Of course I was assuming that we were continuing our discussion about 20-weight oils, and that the differences being discussed are only in the cold viscosity, or the *W number at the beginning. In other words, that we're comparing 0W-20 to 5W-20, as per the OP. I'm well aware that 5W-30 would be different than 5W-20, for example, but that was never the point at hand, and I don't believe I even implied that in my post.

If you really think I'm wrong to claim that 0W-20 is the same viscosity as 5W-20 at operating temperature, that's not my "assumption"! That's straight-up data from the SAE standards, detailed in the sources I referenced. If you're saying SAE standards are wrong, well, I don't have any response to that.

I've revised my post in the quote above to hopefully make myself abundantly clear. Changes are in red.

 

anewhouse:
We're arguing with a belief system/philosophy.
He thinks our assumption is wrong.

Time to move on.

 

You're absolutely right!

I'll admit: I knew I wasn't going to accomplish anything by pushing this point. xkcd: Duty Calls
I'm a scientist and it's hard for me to see people arguing against established facts. I know it happens all the time! But I feel some obligation to present the facts as clearly as possible, so anyone who's actually looking for evidence can have it. Now that that's done, if someone still isn't convinced, there's nothing else I can do. As you said: For some people, once the mind has been made up, facts aren't helpful. Oh, well.

 

I'm a scientist too, but my definition of science is about clarifying the data, challenging assertions, welcoming challenges, and learning something in the process. There was never any hostility intended in the way I challenged your assertion. I thought your assertion was wrong, and I challenged it.

 

I don't know what it's called when you think it's irrational to disagree, with "facts" (maybe denier?) but I'm sure it shouldn't be called "science."

 

Comparing 0W20 to 5W20, they may be more-or-less the same when fully warmed, but how often is that? And how fast do viscosities varies as coolant temp drop?

Watching a ScanGauge on ours, even in our poor excuse for winter, I rarely see coolant temp reach 90C, even on extended drives, with partial grill block. 65~80C is more typical. And if you're doing a lot of short runs, mean coolant temps will be even lower.

 

Multi-grade oils, by their formulation and grading do not behave the same as straight grade oils in terms of their viscosity.
The grading reads as it does because the second number represents the viscosity that the viscosity improvers tend to imitate when the oil reaches operating temperature.
For 5W20 and 0W20, once they reach operating temperature they are approximately the same viscosity as straight 20 weight oil would be at that temperature.

It's all well and good to go around challenging assertions but it's more scientific to do so with something other than to believe differently than established industry norms.

 

I have a feeling that Toyota wouldn't be recommending 0W20 year-round instead of 20W-50 in summer, if it didn't offer some advantage in warmer conditions.

But that's just me.

 

OK! Now that's something interesting, and these observations add a valid point to the discussion. Thanks for sharing. Now we just need to figure out how similarly 0W and 5W oils behave at these typical operating temperatures, rather than the hypothetical operating temperatures presupposed by the SAE standards (100C). Then we could start figuring out how much of a difference this should actually make.
The sources I found and linked above only show viscosity for "cold" (-40 to -30C) and "hot" (100C), not at intermediate temperatures. Does anyone know whether that's been tested and/or published?
Once again, this is primarily to satisfy curiosity, as Toyota's manual is clear in recommending 0W-20, but allowing 5W-20 on a temporary basis.

 

I think we're forgetting that we're talking about tiny incremental differences here. It's harder to get conclusive data, but that doesn't disprove anything.

 

Even in warmer conditions, lower viscosity offers better economy.
I agree with Mendel's point that operating temperature for these cars remains quite low in winter (even with a lower grill block) unless you're at prolonged highway speeds and thus the 5W20 will lower your mileage in that situation.

Did you really mean to type 20W50? I don't care what the temperature--it'll always be more viscous than the grades we're talking about here.

 

I could have typed any oil other than 0W20, but the point I was making is that there's presumed to be a difference, otherwise Toyota wouldn't recommend it.

 

Yes, even a long time ago. You can estimate oil viscosity at intermediate temperatures by interpolating between known points on log paper. There are also complex emperically determined equations (which I can't recall off-hand) for that purpose.

 

We were out and about shopping today, maybe 20 km total. Ambient quite mild, up to 9C. 50% lower grill opening blocked. Coolant never got higher than 65C.

 

You guys belong over at Used Oil Analysis - Bob is the Oil Guy - Bob is the Oil Guy . Endless discussions of various oil specs over there. This is a short civilized discussion by comparison.