Video - Engineering Explained, Do Thin Oils Destroy Engines?

martinq

martinq

Joined
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An excellent review of engine oil viscosity in application in typical Engineering Explained fashion. Clear, concise and wasting no time.

Topics covered:
- boundary, mixed and hydrodynamic lubrication
- GM 6.2 recalls
- NHTSA MPG penalty
- 5w30 / 10w30
- 0w20 / 0w40
- viscosity impact on fuel efficiency
- viscosity impact on engine wear

Edit:
I feel this is a very good, quick overview of the thin vs thick debate along with some great references and examples. I have a some push-back on a couple of points but overall I think this is a very level headed talk on the issues at hand. Very well done, no fluff.

 
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"*Important Note!* I asked a GM powertrain engineer directly about this, who spends his life living and breathing modern performance engines (and specifically small block V8s). Regarding the L87 engine discussed in this video, I asked directly if today's modern, thinner engine oils are too thin for enabling reliability and cause concern of additional engine wear. His answer was a very concise "no." Testing validates this. I think if you watch this video fully (which is quite information dense!), you'll come to understand why. The blame does not lie on the engine oil, as the video breaks down in great detail. Did a lot of research for this one - hope you enjoy it!!"

From cited Honda R&D article:

1748015448282.webp
 
buster said:
"*Important Note!* I asked a GM powertrain engineer directly about this, who spends his life living and breathing modern performance engines (and specifically small block V8s). Regarding the L87 engine discussed in this video, I asked directly if today's modern, thinner engine oils are too thin for enabling reliability and cause concern of additional engine wear. His answer was a very concise "no." Testing validates this. I think if you watch this video fully (which is quite information dense!), you'll come to understand why. The blame does not lie on the engine oil, as the video breaks down in great detail. Did a lot of research for this one - hope you enjoy it!!"

From cited Honda R&D article:

View attachment 280770
Click to expand...
The gm lawyers reminded him to say no. If he said yes then civil suit lawyers would have a smoking gun that gm is deliberately sabotaging peoples engine reliability right from the horses mouth.
 
JavierH19 said:
The gm lawyers reminded him to say no. If he said yes then civil suit lawyers would have a smoking gun that gm is deliberately sabotaging peoples engine reliability right from the horses mouth.
Click to expand...
I doubt it. Plus Honda R&D also supported his claim.

But again, to me it's engine/operating environment dependent.

Fuel dilution can be a problem with some 20 grades though where you're already near the lower threshold.
 
JavierH19 said:
The gm lawyers reminded him to say no. If he said yes then civil suit lawyers would have a smoking gun that gm is deliberately sabotaging peoples engine reliability right from the horses mouth.
Click to expand...
This is always in the back of my mind. No corporation is looking out for the consumer, we exist only to be harvested.

If $$$ = MORE and the risks are LOW ENOUGH then it's always the right decision.
 
buster said:
But again, to me it's engine/operating environment dependent.
Click to expand...
Spot on, I couldn’t agree more!

My new Jeep is a perfect example. Around town the oil stays between 196 and 200 degrees. I’m perfectly comfortable with the recommended 0w20. But when I did some moderate off roading oil temp went to 248 degrees. Now I’m not comfortable with a 20 grade. Settled on a 0w30.
 
buster said:
Fuel dilution can be a problem with some 20 grades though where you're already near the lower threshold.
Click to expand...
Interestingly, when I did the UOA on the 0W-20 after 30,000 miles (using microGreen filters) the viscosity had actually increased to that of about a 30 weight. I have a 2012 Mazda3 with the Skyactiv-G (GDI). So, I actually expected to see a decrease in viscosity.

Edit: The oil used for that run was M1 AFE. These days I use M1 EP HM.
 
I think right comparison isn't BMEP, but the load/area of the bearings in the the connecting rods? Diesel engines run way higher BMEP than many turbo gas engines, at much lower rpm, but the bearings are also built for that, but they aren't putting 0W8 in them yet either.

More useful would be to calculate the actual loads on the bearing and then see how close the manufacturer is pushing limits of the stribeck curve with the recommended oil viscosity with the bearings in that engine at low rpms. I don't think this is a too complicated calculation for a mechanical engineer? Run the numbers and you have an educated guess which engines won't do well with the thinner oil if the additives fail in that oil?
I suspect the motors recommending 0W8 wouldn't handle having an extended OCI with fuel dilution well? But the same motor with 0W20 with fewer additives may take that extended diluted OCI better?

There have been a few turbo gas and diesel engines that can damage the con rod bearings with too much cylinder pressure at low rpms.
The early RAM ecodiesel couldn't be saved by heavier viscosity either? So someone really messed things up somewhere in the design?
 
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Watched the video this early morning. Good informative video. Thought I would post it but changed my mind. The thickies would simply blow it off as YouTube fodder. The thinnies went Whew, when he didn't bash thin oil. so I didn't post it..
 
He still doesn’t completely understand what the numbers on the bottle of oil mean. He’s always referring to the first number as a viscosity but that’s not correct. Lots of people do that, they say things like “the first number in a 5w30 means that it behaves like a 5 grade oil when cold”. Not true at all.
 
I don’t recall him going YT arrogant - so I did not last long in that video …
A quick AI search says 10% of Silverado LT’s have the 6.2L …
Is it that low? I have owned a half dozen 5.3L’s and no 6.2L …
 
He did touch on a point I’ve wondered about: the effect of going outside OEM recommended grades on the hydraulic actuation function of oil within the engine e.g. VCT phasers. There are a lot of BITOG threads pointing out that BMW and Ford recommended oils ranging from 5W-20 to 10W-60 across engines with the same VCT systems with the latter even recommending going from 20 to 40 to remedy phaser problems at one point. That would seem to counter any argument that a thicker oil would somehow be impaired in hydraulic function.

I think he also overlooks the consequences of towing when he compares the 6.2 to the Toyota Camry and RAV4 engines. I doubt the Toyotas do too much of that whereas the 6.2’s probably do a fair bit of towing.

He uses the dreaded F word (flow) when talking about winter grades….at 9m40s (going from a 5W-30 to a 10W-30) “could negatively impact oil flow on cold starts.” I thought only pumpability and to a lesser degree crankability mattered.

It’s fun to nitpick but I found the video entertaining.
 
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his conclusion that thicker oils “can” provide more protection, but are not necessary because thinner oil already provides enough protection. Besides lower MPG and more heat, he did not have any other complaints about thicker oils. Thicker oils provide additional safety margin, even if not needed, I will still take it.
 
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