Truce on Thick Versus Thin

[ZeeOSix]

Thick vs Thin discussions help people better understand how viscosity impacts Tribology. Viscosity will always be a main factor in engine protection and wear.

 

[tired]

Thick vs Thin discussions help people better understand how viscosity impacts Tribology. Viscosity will always be a main factor in engine protection and wear.

Agree. Even though it’s been rehashed a thousand times, I’m sure new people learn a lot every time.

 

[ZeeOSix]

Agree. Even though it’s been rehashed a thousand times, I’m sure new people learn a lot every time.

Here's a study that you and others might be interested in.

J

Thread 'Influence of kinematic and dynamic viscosity on wear shaft in bearing.'

Sep 15, 2025

I've come across an interesting research article by Repsol (Spanish Lubricant Manufacturer) where they tried to develop a wear prediction algorithm. The interesting bit for me come toward the end, where they compare a commercial 0W-20 with full grp IV/V lubricants of differing viscosities and different levels of Viscosty Modifier concentration, in an actual shaft in bearing test.

The research article is called
Wear protection assessment of ultralow viscosity lubricants in
high-power-density engines: A novel wear prediction algorithm

This study shows kinematic viscosity also matters...

• Jetronic
• Replies: 6
• Forum: White Papers and Technical Discussions

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[Gawardawg]

0W20 checking in. I use to be a 20/50 guy. I had to get off that stuff.

 

[kschachn]

It just came to me this morning that there is a place where we could all meet in peace. It seems obvious that we could all use 5W30 synthetic in any application, or alternatively use whatever you wish, but remain silent. Who is is with me? Who will end this “Forever War?” I could use prompt answers as I am going to Wal Mart later in the day.

Or we could just stick with the established physics. As far as I can see that seems to be the biggest problem, feelings and misconceptions instead of science.

 

[kschachn]

Mmm I like 15w40 rotella

Simply the best oil, thick when cold for startup protection and thin and foamy when hot for fuel economy

And lots of vitamins and hths for the fancy cars that want vitamin filled euro oil

don't ban me please

All oils are thick when cold. That’s not where the problem lies.

 

[kschachn]

That 5W-30 oil will never make it through the tight spaces in some modern engines.......ya know

Tolerances, not spaces. C’mon man.

 

[4wd]

Tolerances, not spaces. C’mon man.

Clearance is nice too …

 

[oilburnin]

The reality is that this debate will continue as long as owners manuals omit the temperature chart showing which viscosity to use in which temperature

 

[kschachn]

The reality is that this debate will continue as long as owners manuals omit the temperature chart showing which viscosity to use in which temperature

There’s a reason why the temperature chart is omitted. They are not permitted to print it.

 

[TOLSON]

With the current price of gas, I'll stick with 0W-16

 

[Plumb Bob]

Is this another thick vs. thin thread?

 

[brillo54]

Clearance is nice too …

Do we have clearance, Clarence?

 

[ZeeOSix]

Is this another thick vs. thin thread?

Says so right in the thread title.

 

[tired]

There’s a reason why the temperature chart is omitted. They are not permitted to print it.

Well, it would be expensive to print it.

 

[ZeeOSix]

There’s a reason why the temperature chart is omitted. They are not permitted to print it.

CAFE = Can't Allow Factual Engineering

 

[4wd]

Do we have clearance, Clarence?

Crystal clear

 

[SC Maintenance]

Does this thread mean the thin folks have surrendered?

 

[gfh77665]

CAFE viscosities are for Govt. mpg quotas, not for maximum engine protection.

That said, I don't need a "truce' because I am not at war with anyone, nor ever was.

Everyone is 100% free to run whatever oil and viscosity they want in their vehicles.

I never judge. I discuss and educate when applicable.