Thin or thick (TGMO 0W-20/M1 0W-40): Final verdict

[FCD]

BMW changed the recomendation for the engines TO 10w-60 after they realised some engines were chewing throuh their rod bearings in under 100k miles, they also redesigned the bearingsi think.
This largely solved the problem.
And once your rod bearings are shot no oil will cure that.

 

[FCD]

Originally Posted By: Gokhan
Originally Posted By: ZeeOSix
This paper gives some insight on how different oil viscosity can effect the minimum oil film thickness (MOFT) and the friction losses in engine components.

http://www.eng.auburn.edu/~jacksr7/SAE2002013355.pdf

The only real benefit of thinner oil is a reduction in shearing friction and therefore power loss, which ties into the main CAFE goal to achieve better fuel economy.

As long as the MOFT is still satisfactory (along with whatever anti-wear additives are at play), the wear should be held down to an acceptable level. Thinner oil results in less oil film thickness for engine components to work with (ie, less "safety factor") before metal-to-metal contact occurs. And as mentioned before, if the engine is heavily stressed to elevate the oil temperature well above the "normal" level, then the oil film thickness suffers even more.

The only benefit of thin oil is fuel economy? Really?

The argument that thicker oil has larger MOFT and less wear and thinner oil has smaller MOFT and better fuel efficiency but more wear is primitive and aims to stall the discussion before it gets anywhere. Besides, it's not even correct.

Where should I begin?

Primitive argument: Thicker the oil, larger the MOFT, less the wear.
Reality: Oil too thick = engine damage, as it can result in oil starvation if clearances are not large enough for the viscosity,

Read this thread about the countless engines that had their bearings damaged by running 10W-60, even though it was recommended by the manufacturer. Going down to 0W-40 corrected the problem.

http://www.m3post.com/forums/showthread.php?t=911030

Primitive argument: Thicker the oil, larger the MOFT.
Reality: Perhaps usually true at the bearings but false in general.

Research by Shell indicates thinner oil results in larger MOFT at top piston rings. The reason is that thinner oil flows faster through the ring gaps:

PDF link for the Shell research article

Primite argument: There is no benefit other than fuel efficiency with thinner oil.
Reality: What about more oil flow with thin oil, which results in more oil reaching critical engine parts?
Reality: What about high oil temperature, which is detrimental to engine parts, and the fact that thin oil runs a lot cooler than thick oil thanks to less viscous friction?
Reality: What about cold engine, in which even the thinnest oil is too thick?

This argument just does not hold any water, that thinner oils are better at high temperature because they flow more and have lower oil temps.
There was a guy on here that i think fell for that argument, and used 0W-20 in his Turbo MX-5, the result was a horrible UOA with very high iron.
GM recomends 15W-50 M1 for their Z06 corvettes when being used on the track, and Ford recomend 5W-50 oils for their sportiest cars.
Just recently i saw a Youtube video where a guy ran Redline 0W-20 in a Subaru BRZ i think, and used it on the track, once the engine was getting hotter and hotter, the engine basically did not have any oil pressure, that could not have done anything good for his engine, had he been using say Redline 5W-30 or 0W-40, His oil pressure would have been better, despite probably having slightly higher oil temps.
models, who am i going to trust more, GM amd Ford or some guy on an internet board trying to convince me otherwise...

 

[FlyPenFly]

Thinner oils definitely have their place. Don't make it a crusade. There's example after example of high end cars pushing the boundaries of consumer engineering switching to thicker oils because the applications demand it.

Maybe a thin oil works for you but it's crazy to think that it's the general rule. Maybe you know better than the engine designers and engineers who design and troubleshoot these engines but I doubt it.

It's funny that the example you brought up of BMW directly contradicts the point you're making. BMW had thin oil and then they had to switch to a thicker oil because of reliability problems partially exacerbated by the thin oil. BMW started actively denying warranty claims if you didn't make the switch to 10w60 from the original recommended 5w30 fill.

 

[Gokhan]

Originally Posted By: FlyPenFly
Thinner oils definitely have their place. Don't make it a crusade. There's example after example of high end cars pushing the boundaries of consumer engineering switching to thicker oils because the applications demand it.

Maybe a thin oil works for you but it's crazy to think that it's the general rule. Maybe you know better than the engine designers and engineers who design and troubleshoot these engines but I doubt it.

It's funny that the example you brought up of BMW directly contradicts the point you're making. BMW had thin oil and then they had to switch to a thicker oil because of reliability problems partially exacerbated by the thin oil. BMW started actively denying warranty claims if you didn't make the switch to 10w60 from the original recommended 5w30 fill.

First, regarding BMW, you're misrepresenting the facts. The fix by BMW was not only to increase the viscosity but also to increase the bearing clearance. People actually got far better UOAs by switching to 10W-40 from 10W-60 before they replaced their bearings. You can read it here:

http://www.m3post.com/forums/showthread.php?t=911030

Second, it's crazy to suggest that I recommend 0W-20 for anything from a lawnmower to a locomotive or container-ship engine. Of course, FordCapriDriver's antique car or an 18-wheeler may require thicker oil because the oil pump and oil clearances may not be designed to produce sufficient oil pressure and flow with thinner oil. Also, for certain extreme-load applications, thicker oil may be needed to prevent oil-film collapse at the bearings.

My main point is that most modern engines see no benefit from using thicker oil and in fact they may be worse off with thicker oil in all respects, including both fuel economy and wear.

 

[53' Stude]

Originally Posted By: Gokhan
Originally Posted By: FlyPenFly
Thinner oils definitely have their place. Don't make it a crusade. There's example after example of high end cars pushing the boundaries of consumer engineering switching to thicker oils because the applications demand it.

Maybe a thin oil works for you but it's crazy to think that it's the general rule. Maybe you know better than the engine designers and engineers who design and troubleshoot these engines but I doubt it.

It's funny that the example you brought up of BMW directly contradicts the point you're making. BMW had thin oil and then they had to switch to a thicker oil because of reliability problems partially exacerbated by the thin oil. BMW started actively denying warranty claims if you didn't make the switch to 10w60 from the original recommended 5w30 fill.

First, regarding BMW, you're misrepresenting the facts. The fix by BMW was not only to increase the viscosity but also to increase the bearing clearance. People actually got far better UOAs by switching to 10W-40 from 10W-60 before they replaced their bearings. You can read it here:

http://www.m3post.com/forums/showthread.php?t=911030

Second, it's crazy to suggest that I recommend 0W-20 for anything from a lawnmower to a locomotive or container-ship engine. Of course, FordCapriDriver's antique car or an 18-wheeler may require thicker oil because the oil pump and oil clearances may not be designed to produce sufficient oil pressure and flow with thinner oil. Also, for certain extreme-load applications, thicker oil may be needed to prevent oil-film collapse at the bearings.

My main point is that most modern engines see no benefit from using thicker oil and in fact they may be worse off with thicker oil in all respects, including both fuel economy and wear.


I highly disagree with most of your nonsense and am like KCJEEP and others. You either show facts, and proof that "thicker oils" are bad or stop trying to preach "thin oils are godly"

Thank you and have a good night

 

[CharlieBauer]

Originally Posted By: Gokhan


Research by Shell indicates thinner oil results in larger MOFT at top piston rings. The reason is that thinner oil flows faster through the ring gaps:

PDF link for the Shell research article


That's a real interesting study. Old as well! Thanks for sharing.

 

[Shannow]

Originally Posted By: Gokhan
because the oil pump and oil clearances may not be designed to produce sufficient oil pressure and flow with thinner oil.


Flow and pressure AREN'T providing lubrication...

 

[ZeeOSix]

Originally Posted By: Gokhan

The only benefit of thin oil is fuel economy? Really?

The argument that thicker oil has larger MOFT and less wear and thinner oil has smaller MOFT and better fuel efficiency but more wear is primitive and aims to stall the discussion before it gets anywhere. Besides, it's not even correct.

Where should I begin?

Primitive argument: Thicker the oil, larger the MOFT, less the wear.
Reality: Oil too thick = engine damage, as it can result in oil starvation if clearances are not large enough for the viscosity.
Primitive argument: Thicker the oil, larger the MOFT.
Reality: Perhaps usually true at the bearings but false in general.

Larger MOFT is certainly a good thing with respect to journal bearings because they are soft and sacrificial when metal-to-metal contact occurs. The main goal in a journal bearing is to always have adequate hydrodynamic lubrication with a safe margin in MOFT so contact rarely or never occurs.

Keep in mind that wear rate also has a lot to do with anti-wear additives, especially on boundary or mixed boundary lubricated parts (pistons, rings, cams, chains, etc). If you took away all AW additives and only looked at the wear as a function of viscosity's resulting MOFT, you would see that a larger MOFT is a good thing.

Originally Posted By: Gokhan

Research by Shell indicates thinner oil results in larger MOFT at top piston rings. The reason is that thinner oil flows faster through the ring gaps:

PDF link for the Shell research article

But is the piston ring's MOFT differences enough to make or break what viscosity should be used? Whereas, is the protection difference in other parts of the engine more critical to the oil viscosity and resulting MOFT (ie, journal bearings), and therefore become the main determination on what viscosity is best?

As eluded to before (and mentioned in the paper you linked), it's a balance that should be determined based on the engine's design and the use conditions. Would you run xW-20 in a car used on the track where the oil temperature was constantly in the 275~300 F range? Or would you instead run a xW-50 like so many manufactures of high performance cars recommend for track use, for an obvious reason. Even the simple "what viscosity to use vs expected ambient temperature" chart in your owner's manual is a simple way of the manufacturer saying they recognize that adequate MOFT needs to be maintained to protect the engine when oil temperatures run hotter in hotter climates, even in just normal street driving conditions.

It all boils down to "what's adequate protection" ... so using a xW-20 in a street car designed around xW-20 that never sees oil temperatures above 210~220 F is probably giving "adequate" engine wear protection, but just how much protection margin is left if the engine is pushed much harder?

If you read the "Impact on Durability" section starting on page 20 of the same paper you linked, it says:

Impact on Durability
Durability in Gasoline Engines
The potential disadvantage of moving to lower viscosity lubricants is the thinner oil film that
is expected to exist between lubricated contacts within the engine. However, it should be
remembered that in Europe, current oils have a relatively high viscosity (>3.5 mPa.s)
compared to those marketed in the US and Japan. The move from oils that have High
Temperature High Shear Viscosities (HTHSV) of 3.5 mPa.s to oils with a HTHSV of 2.9
mPa.s is not expected to have a major effect on engine durability for modern gasoline
engines. Indeed, some of these engines may well be running on 2.9 mPa.s oils in the USA or
Japan. Durability may well be of more concern when moving from oils with a HTHSV of
2.9 mPa.s to lower values (e.g. to 2.6 mPa.s).

"In our laboratory, it has been observed that in a modern gasoline engine, well designed
automotive bearings can be lubricated with oils as thin as 2.3 mPa.s without any observable
wear on either con-rod or main bearings."

I think on main reason thicker oils are used in Europe is because the cars there are driven faster and harder in general (ie, Autobahn type use) compared to the US and Japan. Note that engine design is part of the equation on just how well a thinner oil would perform. But on the flip side, using a higher viscosity oil isn't going to hurt in everyday normal street driving. The main drawback would be more shearing friction which slightly hurts fuel economy.

 

[Shannow]

^ +1...what Zee0Six said.

 

[Nickdfresh]

Originally Posted By: Gokhan
Originally Posted By: FlyPenFly
Thinner oils definitely have their place. Don't make it a crusade. There's example after example of high end cars pushing the boundaries of consumer engineering switching to thicker oils because the applications demand it.

Maybe a thin oil works for you but it's crazy to think that it's the general rule. Maybe you know better than the engine designers and engineers who design and troubleshoot these engines but I doubt it.

It's funny that the example you brought up of BMW directly contradicts the point you're making. BMW had thin oil and then they had to switch to a thicker oil because of reliability problems partially exacerbated by the thin oil. BMW started actively denying warranty claims if you didn't make the switch to 10w60 from the original recommended 5w30 fill.

First, regarding BMW, you're misrepresenting the facts. The fix by BMW was not only to increase the viscosity but also to increase the bearing clearance. People actually got far better UOAs by switching to 10W-40 from 10W-60 before they replaced their bearings. You can read it here:

http://www.m3post.com/forums/showthread.php?t=911030

Second, it's crazy to suggest that I recommend 0W-20 for anything from a lawnmower to a locomotive or container-ship engine. Of course, FordCapriDriver's antique car or an 18-wheeler may require thicker oil because the oil pump and oil clearances may not be designed to produce sufficient oil pressure and flow with thinner oil. Also, for certain extreme-load applications, thicker oil may be needed to prevent oil-film collapse at the bearings.

My main point is that most modern engines see no benefit from using thicker oil and in fact they may be worse off with thicker oil in all respects, including both fuel economy and wear.


This is pretty much what I believe. But I would be hesitant to use a, say, 0W-20 in anything not specifically calling for a 20W, I did run 0W-20 in my Opel over the winter...

 

[Nickdfresh]

Originally Posted By: ZeeOSix
...

I think on main reason thicker oils are used in Europe is because the cars there are driven faster and harder in general (ie, Autobahn type use) compared to the US and Japan. Note that engine design is part of the equation on just how well a thinner oil would perform. But on the flip side, using a higher viscosity oil isn't going to hurt in everyday normal street driving. The main drawback would be more shearing friction which slightly hurts fuel economy.


They Autobahn is only in one country, although I think there are other high speed motorways elsewhere...

I was under the impression that longer drain intervals and high oil costs are the biggest reasons that Europeans tend to have thicker oils in their sumps. When oils moved to SJ and the first 5W-20's came out, a Valvoline engineer stated in an interview in a trade publication that she always recommended using thinner oils where appropriate because the base oils (in "conventionals") the 5W-XX were receiving the most R&D...

 

[ZeeOSix]

Originally Posted By: Nickdfresh
Originally Posted By: Gokhan
... regarding BMW, you're misrepresenting the facts. The fix by BMW was not only to increase the viscosity but also to increase the bearing clearance.

I would be hesitant to use a, say, 0W-20 in anything not specifically calling for it.


As seen in this graph, a thicker oil will always give a greater MOFT in bearings regardless of their clearance. But a xW-20 is sensitive to the correct bearing clearance in order to maximize the MOFT.

This is why using xW-20 in engines not specifically designed for it could be bad, and why using a thicker oil in engines specifying Xw-20 isn't as critical.

http://www.substech.com/dokuwiki/doku.php?id=ecological_aspects_of_engine_bearings

 

[Gokhan]

Originally Posted By: ZeeOSix
"In our laboratory, it has been observed that in a modern gasoline engine, well designed automotive bearings can be lubricated with oils as thin as 2.3 mPa.s without any observable wear on either con-rod or main bearings."

Which is one of the main points of this thread, the other main points being the lubrication advantages for the upper end of the engine (such as the top piston ring in the article or similarly the valvetrain as in my UOA) and fuel-economy benefits of thinner oil.

 

[ZeeOSix]

More info on thin vs thick: http://machinerylubrication.com/Read/518/motor-oils

 

[ZeeOSix]

Originally Posted By: Gokhan
Originally Posted By: ZeeOSix
"In our laboratory, it has been observed that in a modern gasoline engine, well designed automotive bearings can be lubricated with oils as thin as 2.3 mPa.s without any observable wear on either con-rod or main bearings."

Which is one of the main points of this thread, the other main points being the lubrication advantages for the upper end of the engine (such as the top piston ring in the article or similarly the valvetrain as in my UOA) and fuel-economy benefits of thinner oil.


Look at what I posted above about MOFT vs oil viscosity vs bearing clearance. Using xW-20 in an engine not specifically designed for it (like yours) might not be the best idea in terms of wear protection in certain engine components like the journal bearings - especially if the engine is ever pushed hard.

 

[Gokhan]

Originally Posted By: ZeeOSix
Originally Posted By: Nickdfresh
Originally Posted By: Gokhan
... regarding BMW, you're misrepresenting the facts. The fix by BMW was not only to increase the viscosity but also to increase the bearing clearance.

I would be hesitant to use a, say, 0W-20 in anything not specifically calling for it.


As seen in this graph, a thicker oil will always give a greater MOFT in bearings regardless of their clearance. But a xW-20 is sensitive to the correct bearing clearance in order to maximize the MOFT.

This is why using xW-20 in engines not specifically designed for it could be bad, and why using a thicker oil in engines specifying Xw-20 isn't as critical.

http://www.substech.com/dokuwiki/doku.php?id=ecological_aspects_of_engine_bearings



Most modern engines, including my 85 Corolla and a BMW M3, which were "designed" for 10W-30 to 20W-50 and 10W-60, respectively, have a bearing clearance of about 0.001 in. Moreover, you didn't realize that the bottom of that graph is not 0 but 20 µin. Therefore, there isn't a huge difference between 0W-20 vs. 10W-60 -- about 25 vs. 30 µin -- each providing adequate lubrication -- assuming this graph applies to pertinent engines and RPM/torque regimes.

Heavy-duty (18-wheeler etc.) engines require large bearing clearance and large MOFT, therefore high oil viscosity, because of abrasive soot particles, which may otherwise be larger than the MOFT. Older, dirty-running gasoline engines, especially with bad bearing designs, may be similar to heavy-duty engines in this respect.

 

[ZeeOSix]

^^^ Never said the bottom of the scale was 0, so how would you know what I realized or not. In journal bearings, a 50 to 100% increase in MOFT could mean the difference between contact or not, especially if oil temps are well above normal.

 

[FlyPenFly]

Lol 85 Corolla, modern M4, same 0w20 oil no problem. If you believe that there's no further discussion necessary.

 

[ZeeOSix]

Originally Posted By: Gokhan
Research by Shell indicates thinner oil results in larger MOFT at top piston rings. The reason is that thinner oil flows faster through the ring gaps.

PDF link for the Shell research article


I forgot to mention earlier ... apparently it didn't help reduce the ring wear because your chromium showed higher particle counts with the 0W-20 vs the 0W-40.

0W-40 = 2.1 ppm Cr
0W-20 = 2.6 & 5.5 ppm Cr

 

[Gokhan]

Originally Posted By: ZeeOSix
^^^ Never said the bottom of the scale was 0, so how would you know what I realized or not. In journal bearings, a 50 to 100% increase in MOFT could mean the difference between contact or not, especially if oil temps are well above normal.

Well, that's only about a 30% increase or less in that plot for the relevant bearing clearances of modern engines (10 - 50 µm = 0.4 - 2 µin).

Also, see this thread below. Thicker oil (10W-60) can increase MOFT collapse and bearing damage over thinner oil if the bearing clearance is too small. Real physics (real world) is more complicated than that simple graph and thicker oil starts hurting at one point toward the left of the graph instead of helping. That's why empirical data is more valuable than simple theory.

Castrol Edge 10w-60, 14k,'09 BMW M3

"I know my lead is high at 18. I'm hoping my switch to castrol 0w40 will improve my lead count. Other M3 drivers have switched to a 0w40 oil and cut their lead levels in half. I'm going to pull a sample at 5k and see if my numbers improve."

...