Which engine part will wear first from using too thin oil?

[meep]

Chrysler study I read years ago concluded that the valve trains held up better with thinner oils, and the bottom end fared better with heavier oils. It was an interesting study, especially when it came to the chain. The timing chain needed a few Rpm before its lubrication became hydrodynamic. The viscosity of the oil mattered here. If I recall, 5-30 needed about 1350 rpm to become hydrodynamic in their test mule. This was 15 years ago so it was a different crop of motors than we have now.

Today’s engines prefer tall gearing, low rpm strategies that keep the throttle as far open as possible to reduce pumping losses. This exposes the chain set to lower operating rpm with more tension. I used to be in the pro-chain camp, but with all of the tensioner and guide problems we’ve seen in the past decade, I’ve been leaning my preference back to belts, if I was asked for a vote.

My truck has chains. And it has a little startup clatter. Oh well.

 

[ZeeOSix]

The common theme in these studies is that the piston rings are the most sensitive part of the engine to increased wear from thin oil grades. This is because the oil film at the rings can approach the temperature of the rings and upper cylinder liner, which get very hot at high engine loads. Shear rates are also high at the piston rings.

Bingo

 

[ZeeOSix]

Rod bearings, for sure-they're always the first to go...

I would say in this order:
Piston rings/liners
Upper rod bearings

Yes, rod bearings are very soft compared to rings, so when they are put under high loads and the oil is too hot and thin to maintain adequate MOFT they will wear. They can show wear way before they start making any noise ... like these shown in the 1st photo below. The 2nd rod bearing photo shows much more wear. Rings are really hard metal, and they can tolerate less oil film thickness, and when they do wear they just spring out against the cylinder as they wear, so they could wear quite a bit too without any noticeable ramifications.

 

[ZeeOSix]

I've read thin oils remove heat better from rod and main bearings due to more oil flow. Seems reasonable.

Doesn't make any real difference in terms of "removing heat better" - if it does, it's minor (a few degrees) because the flow difference is minuscule. If thin oil was good for journal bearings then manufacturers of high performance track cars wouldn't say to use a thicker oil for track use. Nor would Toyota say in the OM that thicker oil will provide more protection in server use conditions.

 

[ZeeOSix]

I would assume the wear rate is dependent on metallurgy, heat treatment, oil flow and cooling to the part, and OCI.

And also the viscosity ... specifically the HTHS viscosity.

 

[ZeeOSix]

yes and that wasn't even 0W-5 as that spec didn't and doesn't exist.

The KV100 and HTHS was so low that it would have fit in to around a 5 grade if it was defined in SAE J300.

 

[hid3]

I've dismantled several tens of (VW) diesel engines. Usually rod bearings are fine, worst case with a few spots of slight darker grey discoloration (but nothing serious), whereas main bearings are always pristine, just like new. One wouldn't say they were used at all. All of this is for engines with unknown maintenance history and those engines have covered well over 300'000 km and failed for some other reasons (TB break, dropped valve, broken conrod, dropped valve seat, hydrolock, etc). At over 250k km mark there's usually noticeable cylinder crosshatch wear, if it's gone completely then certainly engine has covered more than 300k

 

[ZeeOSix]

I've dismantled several tens of (VW) diesel engines. Usually rod bearings are fine, worst case with a few spots of slight darker grey discoloration (but nothing serious), whereas main bearings are always pristine, just like new. One wouldn't say they were used at all. All of this is for engines with unknown maintenance history and those engines have covered well over 300'000 km and failed for some other reasons (TB break, dropped valve, broken conrod, dropped valve seat, hydrolock, etc). At over 250k km mark there's usually noticeable cylinder crosshatch wear, if it's gone completely then certainly engine has covered more than 300k

And what oil viscosity were those engines specified to use?

 

[hid3]

And what oil viscosity were those engines specified to use?

Assuming (but only assuming) the correct oil was used, it should have been either VW 505.01 5w-30/5w-40 or VW 504.00/507.00 5w-30 (by that time 0w-30 was still not approved for 504/507 spec); as you probably know, VW 504/507 oil is "on the heavy side of 30", I think spec calls >11.8 cSt at 100 *C

 

[Jetronic]

The KV100 and HTHS was so low that it would have fit in to around a 5 grade if it was defined in SAE J300.

7.4 cSt @ 212°F is all I could dig up, and that puts it square in the 20 range.

 

[ZeeOSix]

7.4 cSt @ 212°F is all I could dig up, and that puts it square in the 20 range.

KV100 = 4.6 cSt.
HTHS = 1.59 cP

Thread 'Upcoming 0W5 Grade Red Line Oil Experiment- 2019 Lincoln Navigator 4WD 3.5L V6 Twin Turbo'

Jan 18, 2023

Engine: This Black Label version of the Navigator has a 3.5L, 450-hp twin-turbo V-6 pushing an over 3 ton barn door through the wind. It has 9k towing capacity and specs a 5W30 motor oil. It is mated to a 10-speed automatic transmission. The package gets you to 60 MPH in 5.4 seconds. Correct me if am wrong - I think the twin turbos are of different sizes to minimize turbo lag, a small turbo and a large turbo to better cover the RPM range more efficiently.

Test Conditions:
The car had around 28,000 miles when the 5 grade oil was put into it, 29,000 when I took out the oil. The oil filter...

• AEHaas
• Replies: 198
• Forum: Passenger Car Motor Oil (PCMO) - Gasoline Vehicles

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[Jetronic]

so h was not using the NEO 0w-5 then? that ne has a VOA posted here with 7.4 cSt viscsity

 

[Cujet]

Toyota coats their Dynamic Force Engine's upper compression and oil piston rings with diamond like carbon (DLC).

DLC is great, right up until it isn't. Just like any other coating or hardening, a lack of sufficient film strength can result in DLC coating wearing through. At which point rapid failure is next.

I think the only consensus is that the timing chain doesn't care too much about viscosity.

Timing chains wear considerably faster with low viscosity oils, we've known for a long time that a clean 30 viscosity oil results in the longest chain life. This is why top manufacturers that spec lower viscosity oils now use coated timing chain pins. It is also why Ford moved back up to 5W-30 in the F150 engines.

 

[ZeeOSix]

so h was not using the NEO 0w-5 then? that ne has a VOA posted here with 7.4 cSt viscsity

NEO "false advertising" since it would have to have a KV100 of around 4 cSt to be around a 5 grade.

 

[Gene K]

yes but it's something like 8.3 cst viscosity at 212°F. Neo 0W-5 iirc

Is that a typo? That's a 20 Grade.

 

[Jetronic]

Is that a typo? That's a 20 Grade.

That was from an oil analysis. Someone used it in a Golf TDI.