OCI, not when but why?

[customboss]

4 hours ago, Grumpy Bear said:

 

It has been shown that increased viscosity does not physically harm a motor nor interfere with hydraulic function of cam phasers. 

Depends on system 

[Grumpy Bear]

39 minutes ago, customboss said:

Depends on system 

 

Somehow I knew this was coming. Dirt in the water. 

 

This is an example of a select point of data removed from context can create a situation outside of practical operation. And offered without context, example. A simple statement said as if it's offer in and of itself is proof. 

 

As a child grandpas Studebaker was treated to a tin of hot coals placed under the oil pan, transmission and differential for several hours to bring those mineral based straight weights cut by API Gravity alone (ISO scale) to a liquid state thin enough to pump and cling. Any effort short was an open invitation to disaster. Moving on to my fathers time, and offered more than once in these treads, are the examples of dad's business benefiting from such fool hardy operation as to require the replacement of oil pump hex shafts or even main/rod bearings when such fools ratted their motors full of 10W30 on -25 F days during the first few minutes of operation. 

 

Today 5W*** is then enough on those same -25 F days to be driven off withing only the time it takes to get oil pressure with a judicious foot and prudent operation for a few miles. Coal no longer required and the use of Group PAO's offering much lower cold temperature viscosities than even the PPD added Group II's. (Not very effective on Group III's and no where near the same low temperature performance by THOUSANDS of Cp). 

 

 

Automatic transmissions, primarily hydraulic devices often act funny until the fluid is up to about 60 F, can kill a CVT,  then function the same anywhere between that point and fluid failure temperature. Huge difference between cold weather viscosity appropriately selected and that of a fluid operating at any normal sustained operating temperature. The 4 cSt  Idemitsu/Mitsubishi vs Red Line 6 cSt CVT fluid increase is a non issue hot and a very big help cold. Several thousand cP verses 20 cP differential cold.

 

There is more difference than five grades at normal operating temperatures than between an SAE 30 operating between 180 F vs 240 F. Keep the W number the same and any and all augments counter vanish into reality. 

 

Interestingly and as a aside. Chevy, Hudson used poured babbitt bearings into the 50's. Prewar the Stovebolt 6 manual said 20W winter for the 216 CID and SAE 30 for the bigger motors summer. Today bearing and bore life has been increased by multiples using 15W40, 20W40 and 20W50. There is not softer bearing and they don't wash out using heavy oils. 

 

This sort of counter reality comments are not helpful. 

[customboss]

24 minutes ago, Grumpy Bear said:

 

Somehow I knew this was coming. Dirt in the water. 

 

This is an example of a select point of data removed from context can create a situation outside of practical operation. And offered without context, example. A simple statement said as if it's offer in and of itself is proof. 

 

As a child grandpas Studebaker was treated to a tin of hot coals placed under the oil pan, transmission and differential for several hours to bring those mineral based straight weights cut by API Gravity alone (ISO scale) to a liquid state thin enough to pump and cling. Any effort short was an open invitation to disaster. Moving on to my fathers time, and offered more than once in these treads, are the examples of dad's business benefiting from such fool hardy operation as to require the replacement of oil pump hex shafts or even main/rod bearings when such fools ratted their motors full of 10W30 on -25 F days during the first few minutes of operation. 

 

Today 5W*** is then enough on those same -25 F days to be driven off withing only the time it takes to get oil pressure with a judicious foot and prudent operation for a few miles. Coal no longer required and the use of Group PAO's offering much lower cold temperature viscosities than even the PPD added Group II's. (Not very effective on Group III's and no where near the same low temperature performance by THOUSANDS of Cp). 

 

 

Automatic transmissions, primarily hydraulic devices often act funny until the fluid is up to about 60 F, can kill a CVT,  then function the same anywhere between that point and fluid failure temperature. Huge difference between cold weather viscosity appropriately selected and that of a fluid operating at any normal sustained operating temperature. The 4 cSt  Idemitsu/Mitsubishi vs Red Line 6 cSt CVT fluid increase is a non issue hot and a very big help cold. Several thousand cP verses 20 cP differential cold.

 

There is more difference than five grades at normal operating temperatures than between an SAE 30 operating between 180 F vs 240 F. Keep the W number the same and any and all augments counter vanish into reality. 

 

Interestingly and as a aside. Chevy, Hudson used poured babbitt bearings into the 50's. Prewar the Stovebolt 6 manual said 20W winter for the 216 CID and SAE 30 for the bigger motors summer. Today bearing and bore life has been increased by multiples using 15W40, 20W40 and 20W50. There is not softer bearing and they don't wash out using heavy oils. 

 

This sort of counter reality comments are not helpful. 

None of those examples had VVT or cam phasing. Be careful making blanket statements. 

[OnTheReel]

I can’t think of a single engine that HAS had issues with VVT on a higher viscosity oil. Within reason is my asterisk, as always.
 

If changes in viscosity bricked the systems you’d expect every VVT engine to either run like ****** when cold or run like ****** when hot. Or both. Same goes for AFM/DFM/MDS systems.

 

FWIW…-5* this morning, Red Line 0w40 in the Jeep. Happy camper. Fired right up and cam phasers didn’t even rattle. Good batteries, good oil, no problems.

[customboss]

1 hour ago, OnTheReel said:

Within reason

 

[customboss]

Tired of be sprayed in oil drain? 
 

 

[Grumpy Bear]

5 hours ago, customboss said:

None of those examples had VVT or cam phasing. Be careful making blanket statements. 

 

Every automotive example I've worked on since 1998 had VVT (save my 3800), which BTW is cam phasing. Honda, Mitsubishi, Ford, GM.

 

The others mentioned, babbitt motors, were "heavy oil causes wear' samples, which it did not and now common place in those arenas.  

 

3 hours ago, OnTheReel said:

I can’t think of a single engine that HAS had issues with VVT on a higher viscosity oil. Within reason is my asterisk, as always.
 

If changes in viscosity bricked the systems you’d expect every VVT engine to either run like ****** when cold or run like ****** when hot. Or both. Same goes for AFM/DFM/MDS systems.

 

FWIW…-5* this morning, Red Line 0w40 in the Jeep. Happy camper. Fired right up and cam phasers didn’t even rattle. Good batteries, good oil, no problems.

 

You can remove 'within reason' for the reasons you stated. Viscosity is temperature dependent running in normal course of operations 60,000 cP at -40 C pumping viscosity to now 1.7 cP at 150 C, HTHS. VVT/DFM/AFM works fine. Your argument is sound. Wear is another issue but function unaltered. 

 

Even Lee recently suggested I try Red Line 5W50 in the Mitsubishi 3A92 which calls for 0W20 in an attempt to build frictional heat. RIGHT? 

 

Could there be some 'jewel-box' bellows type oiling system such as used on steam turbines in an automotive application I'm am unaware of that would be quite viscosity sensitive? I guess. Anyone care to name one? 

 

And there are "spray bore" motors, such as the latest Ford Mustang V8's that due to the finish of spray bores are harmed not from the viscosity causing wear BUT from oil migration and calcium carry causing detonation. Or so the claim lies. 

 

************************************** 

 

I've run 10W40 in air cooled Harley motors requiring 20W50 (with coolers) with lower wear metals and 5W40 in Mitsubishi motors requiring 0W20 with lower wear metals. Point is? Heavy is always best but it is more often than not better. Testing will sort that out if your patient enough to extract that result. 

 

The worst thing that happens is you use a bit more gas if it's to heavy. Early wear out is the worst that happens when to light. For me. it's a good trade and more often than not a motor that actually benefited from additional viscosity ALSO gave better fuel economy!! 

Edited December 14, 2025 by Grumpy Bear

[OnTheReel]

Yeah, by “within reason” I more or less meant NOT using an oil with an inappropriate winter rating for your climate. Like 15w40 in Siberia. If the concern is excessive viscosity hindering function, or causing damage, that’s really the only type of scenario I could see.
 

I also think “within reason” should exclude…say…running 10w60 in the Mitsubishi. Doubt that would even affect VVT function but at some point it just seems gratuitous based on engine design, output, load, etc...

[Atlas]

So...should I be ignoring GM's insistence on 0w20 in my 3.0 diesel? Just give 'er the 15w40?

[Grumpy Bear]

11 hours ago, OnTheReel said:

Yeah, by “within reason” I more or less meant NOT using an oil with an inappropriate winter rating for your climate. Like 15w40 in Siberia. If the concern is excessive viscosity hindering function, or causing damage, that’s really the only type of scenario I could see.
 

I also think “within reason” should exclude…say…running 10w60 in the Mitsubishi. Doubt that would even affect VVT function but at some point it just seems gratuitous based on engine design, output, load, etc...

 

Excellent points both. The oil must be pumpable indeed so yes, 15W/20W/25W is a non starter unless you use coal like my grandfather To clairify. I was speaking about the second number *W20/40/50

 

The 10W60 example in my area might conceivably place Raven in the yellow circle, agreed and unduly waste fuel. Targeting the green area is well enough. However if I lived in Syria where 20W50 is already the book spec visiting the 10W60 for a look would harm nothing. Standard oil for the BMW M series. The object is lowest wear even at the sacrifice of fuel but wasting it just to waste it is a waste  

Graph credits to

Recent Developments in Wear Prevention, Friction and Lubrication, 2010:263-278

ISBN: 978-81-308-0377-7 Editor George K Nikas

Green & Yellow markups my own

 

 

Edited December 14, 2025 by Grumpy Bear

[Grumpy Bear]

@Atlas, saw your question on the forums page. 

 

I haven't done a lot of looking about for diesel engines but I know that the PF system is VERY finicky which sticks a pin in many commercial diesel oils. I also don't know where you live so not sure if 15W* is appropriate. Both of these place some limits on selection. I also don't know the milage of your engine. But wear reduction MAY be improved with a DEXOS D 5W30. 

 

AMSOIL DP530 looks like a winner. HTHS of 3.5 cP, low ash and excellent cold weather and turbo clean properties. AMSOIL tends to use a very shear stable polymer. 

 

All that said, testing would be the only way to know. Keep in mind that the improvement in bore wear doesn't come from the 100 C temperature viscosity but rather the HTHS viscosity with limited improvement beyond 3.5 cP. A carefully selected *W30 can meet that and your Diesel Particulate filter requirements as well. 

 

 

 

 

[customboss]

5 hours ago, Atlas said:

So...should I be ignoring GM's insistence on 0w20 in my 3.0 diesel? Just give 'er the 15w40?

No stick with GM recommendation for sure. As if you didn’t know that. 

[Black02Silverado]

5 hours ago, Atlas said:

So...should I be ignoring GM's insistence on 0w20 in my 3.0 diesel? Just give 'er the 15w40?

Stay with 0w-20. It’s in thousands of 3.0’s and some are high mileage. No worries. 

[Grumpy Bear]

And exactly what grave danger will befall the 3.0 with an increase in HTHS viscosity? Give me ya' all's best horror story. 

 

 

I want to hear TRUE SCIETIFICALLY VERIFIEABE experiences of 3.0 motors failing and traceable solely to higher HTHS viscosity. 

 

I already gave scholarly articles that PROVE it WILL reduce wear. The trade is fuel economy...sometimes. 

 

[OnTheReel]

12 hours ago, Grumpy Bear said:

However if I lived in Syria where 20W50 is already the book spec visiting the 10W60 for a look would harm nothing. Standard oil for the BMW M series. The object is lowest wear even at the sacrifice of fuel but wasting it just to waste it is a waste  

People speculate that BMW went to 10w60 due to the frequent rod bearing failures on the M-cars. A tactic GM tried recently with much less success.

 

BMW has since moved to 0w40 for the most part. But they ran 10w60 for awhile and bearing issues subsided. Not saying it was the only fix but bet it helped…