Do you think thick oil always protects rings better? Think cavitation!

[CourierDriver]

thicker oil is just a concept---ugh you gotta an oil pump on your car--ugh it can only pump so many gallons a minute thru your engine-ugh,,the joy of physics.

but what the mind can conceive, it will believe...marketing is a great tool.

 

[Eddie]

Thank you Gokhan for the interesting information. I found it a very interesting read. Ed

 

[TurboLuver]

Originally Posted by Gokhan
Unlike bearing lubrication, cylinder - ring lubrication is very complicated that involves all regimes of lubrication, including boundary, mixed/elastohydrodynamic, and hydrodynamic.

While thicker oil tends to provide a thicker oil film in general, especially in the hydrodynamic region, it turns out that the oil flow by the rings is very complicated and cavitation -- a complete break in the oil film -- is always present and inevitable regardless of the viscosity and operating conditions.

It turns out that the length of the cavitation (oil-starved) region is proportional to (see the second article):

Length of the cavitation ring section ~ (RPM x viscosity)^0.3

^0.3 represents the 0.3rd power, which reduces the effect of the RPM and viscosity. For example, if you increase the viscosity by 2, cavitation length increases by 23% and not by a factor of 2.

Typical cavitation lengths (oil-film-starved sections) are around a millimeter or less.

This means you need to strike the right balance between cavitation and oil-film thickness. Going thicker won't necessarily reduce ring wear. Cold engines could be even more problematic for thicker oil.

The first link is open access:

https://www.sciencedirect.com/science/article/pii/S0301679X15001760

Not open access:

http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1468067

So, it's something to think about before you go arbitrarily thick to reduce ring wear.





Is this theory only or was it proven in practice as well?

 

[badtlc]

This intuitively make sense to me when you also consider the other studies posted here recently showing that lower viscosity may be better for high RPM applications and thicker viscosity could be better for lower RPM applications. This can help explain those results.

 

[PimTac]

What if the rings are bi-directional? My Mazda has these.

 

[CT8]

Basically let the engine/oil warmup before whomping on the gas pedal. Cold oil is thick, hot oil is thin. Then hope the parts were engineered properly. Cavitation happens on boat propellers and they run in water.

 

[tig1]

Originally Posted by double vanos
Rings? That's the last of my worries! My concerns are the timing chains; thicker oils protect them better ( I hope).


The timing chains in my Fords that call for a 20wt oil have all been very quite using 0-20 M1 at 10K OCIs.

 

[1978elcamino]

Originally Posted by demarpaint
Here we go again, I'll play. I seriously doubt 5W30 in a vehicle calling for 5W20 is going to cause any phenomenon that will cause damage to my engines. In my case I believe it will benefit the engine over time. In fact I doubt a 40 grade oil will be a problem either.


I can probably add an example to substantiate this. Most Ford 3v 5.4 modular engines have serious timing component issues all derived from oil pressure. My fathers 2008 has 290k on the clock has only seen 10w30 synthetic since new. No phaser knock, no codes or repairs to the engine except plugs and only rattles for a second or two when cold in the morning. Were in Florida where it never gets cold but a couple days a year. Now, Im not claimig that this is the fix all cure all for this motor, but most mod motors running 5w20 all their life have needed a complete timing set by this mileage, or at least a set of phasers or guides. My personal 2v 4.6 I just sold with 240k had 10w40 its whole life and never made cold start chain slap unless I pushed oil past 6500 miles. This only happened a couple times due to trips out of town being in the interstate for hours at a time. My brother in law now owns it and his teenage son drives it.

 

[BigShug681]

So does this mean my truck, which runs on 15w40 and 10w30, is on its last leg? I have 211k miles on the clock and zero blow by, so my rings can't be damaged that badly.

 

[1978elcamino]

Originally Posted by BigShug681
So does this mean my truck, which runs on 15w40 and 10w30, is on its last leg? I have 211k miles on the clock and zero blow by, so my rings can't be damaged that badly.


Haha, not if its your PSD, it has hundreds of thousands of miles left.

 

[dave1251]

Originally Posted by OilUzer
You can blindly & safely pick 0Wx30 (or even 0Wx40) for all passenger cars/trucks on this planet with no issues. Racing excluded ...

You can't say the same about 0Wx16 or 0Wx20



You can say neither example is not vaild if the cooling system is not up to snuff. I doubt you can explain the thickness of CST.

 

[dave1251]

Originally Posted by 1978elcamino
Originally Posted by demarpaint
Here we go again, I'll play. I seriously doubt 5W30 in a vehicle calling for 5W20 is going to cause any phenomenon that will cause damage to my engines. In my case I believe it will benefit the engine over time. In fact I doubt a 40 grade oil will be a problem either.


I can probably add an example to substantiate this. Most Ford 3v 5.4 modular engines have serious timing component issues all derived from oil pressure. My fathers 2008 has 290k on the clock has only seen 10w30 synthetic since new. No phaser knock, no codes or repairs to the engine except plugs and only rattles for a second or two when cold in the morning. Were in Florida where it never gets cold but a couple days a year. Now, Im not claimig that this is the fix all cure all for this motor, but most mod motors running 5w20 all their life have needed a complete timing set by this mileage, or at least a set of phasers or guides. My personal 2v 4.6 I just sold with 240k had 10w40 its whole life and never made cold start chain slap unless I pushed oil past 6500 miles. This only happened a couple times due to trips out of town being in the interstate for hours at a time. My brother in law now owns it and his teenage son drives it.



We have a 5.4 here work 130K miles needing cam phasers and all it had as a oil grade is 10W30 at 5K OCI's. It not grade nor service interval it is literally luck of the draw.

 

[Y_K]

Cavitation was always a very serious factor in pumps, but unless you are not running a racing car with above redline rpm for most of its useful life, piston ring cavitation is the least of worries.

Pitting we may see on a water pump impeller is a great and easy to digest illustration of damage from cavitation. It is a big issue in industrial hydraulic pumps.

 

[Virtus_Probi]

This is actually very interesting to me...I don't think there's a suggestion of quick engine failure due to cavitation around the rings, but maybe this is one spot where a thicker oil might have some tiny negative effect at operating temp. But maybe not, based on Shannow's comment about the area not really being dry but still retaining a film.
I guess if this was really an overwhelming issue, a cold engine at startup would really be in trouble...unless there is microheating around the rings and the oil there is always much hotter than the sump temp.

 

[Omahaug]

Okay so in theory if this were true, what's in actual practice or implementation? Is is demonstrably true that engines using thicker oils have worn rings or cylinder walls? Does this state what the thickness threshold is where this is actually a problem? Does the wear actually translate to some loss in engine lifespan or change in compression?

My bet is none of this matters and that you'd have to use an absurdly "thick" oil to get the kind of wear, wear that is probably nanometers thick.

It's not like this is going to be referring to the difference between Xw-20 to Xw-30, or even Xw-16 to Xw-50, if that kind of change is going to rub your piston rings dry, remove all of the honing on the walls or bore the cylinder out, then I'm a kangaroo.

I don't think any of this also factors into account the low friction coatings they apply to cylinder walls and pistons rings these days, to eke out better fuel mileage.

 

[WyrTwister]

Never thought of thick opil in relationship to rings . Mostly for noisy top ends and loose / worn bearings .

 

[buster]

Shell published a study back around 2003 that showed 20 grade oils provided a thicker film around the rings than a comparable 30 grade. I haven't taken the time to really look into it myself so I don't know the details.

 

[dogememe]

Originally Posted by 1978elcamino
Originally Posted by demarpaint
Here we go again, I'll play. I seriously doubt 5W30 in a vehicle calling for 5W20 is going to cause any phenomenon that will cause damage to my engines. In my case I believe it will benefit the engine over time. In fact I doubt a 40 grade oil will be a problem either.


I can probably add an example to substantiate this. Most Ford 3v 5.4 modular engines have serious timing component issues all derived from oil pressure. My fathers 2008 has 290k on the clock has only seen 10w30 synthetic since new. No phaser knock, no codes or repairs to the engine except plugs and only rattles for a second or two when cold in the morning. Were in Florida where it never gets cold but a couple days a year. Now, Im not claimig that this is the fix all cure all for this motor, but most mod motors running 5w20 all their life have needed a complete timing set by this mileage, or at least a set of phasers or guides. My personal 2v 4.6 I just sold with 240k had 10w40 its whole life and never made cold start chain slap unless I pushed oil past 6500 miles. This only happened a couple times due to trips out of town being in the interstate for hours at a time. My brother in law now owns it and his teenage son drives it.


So, the Crown Vic I just bought has been serviced with 5w-30 synblend according to the receipts from the police department from 0 to 150k miles when they sold it. I bought it with 165k or so. I plan to use 0w-30 - you think that'll be ok? I know you're talking about a 3v and I'm talking about a 2v but I'm just curious.

 

[aquariuscsm]

Originally Posted by dogememe
Originally Posted by 1978elcamino
Originally Posted by demarpaint
Here we go again, I'll play. I seriously doubt 5W30 in a vehicle calling for 5W20 is going to cause any phenomenon that will cause damage to my engines. In my case I believe it will benefit the engine over time. In fact I doubt a 40 grade oil will be a problem either.


I can probably add an example to substantiate this. Most Ford 3v 5.4 modular engines have serious timing component issues all derived from oil pressure. My fathers 2008 has 290k on the clock has only seen 10w30 synthetic since new. No phaser knock, no codes or repairs to the engine except plugs and only rattles for a second or two when cold in the morning. Were in Florida where it never gets cold but a couple days a year. Now, Im not claimig that this is the fix all cure all for this motor, but most mod motors running 5w20 all their life have needed a complete timing set by this mileage, or at least a set of phasers or guides. My personal 2v 4.6 I just sold with 240k had 10w40 its whole life and never made cold start chain slap unless I pushed oil past 6500 miles. This only happened a couple times due to trips out of town being in the interstate for hours at a time. My brother in law now owns it and his teenage son drives it.


So, the Crown Vic I just bought has been serviced with 5w-30 synblend according to the receipts from the police department from 0 to 150k miles when they sold it. I bought it with 165k or so. I plan to use 0w-30 - you think that'll be ok? I know you're talking about a 3v and I'm talking about a 2v but I'm just curious.


If it were my Crown Vic I'd run 10W30 in it.

 

[dave1251]

Originally Posted by aquariuscsm
Originally Posted by dogememe
Originally Posted by 1978elcamino
Originally Posted by demarpaint
Here we go again, I'll play. I seriously doubt 5W30 in a vehicle calling for 5W20 is going to cause any phenomenon that will cause damage to my engines. In my case I believe it will benefit the engine over time. In fact I doubt a 40 grade oil will be a problem either.


I can probably add an example to substantiate this. Most Ford 3v 5.4 modular engines have serious timing component issues all derived from oil pressure. My fathers 2008 has 290k on the clock has only seen 10w30 synthetic since new. No phaser knock, no codes or repairs to the engine except plugs and only rattles for a second or two when cold in the morning. Were in Florida where it never gets cold but a couple days a year. Now, Im not claimig that this is the fix all cure all for this motor, but most mod motors running 5w20 all their life have needed a complete timing set by this mileage, or at least a set of phasers or guides. My personal 2v 4.6 I just sold with 240k had 10w40 its whole life and never made cold start chain slap unless I pushed oil past 6500 miles. This only happened a couple times due to trips out of town being in the interstate for hours at a time. My brother in law now owns it and his teenage son drives it.


So, the Crown Vic I just bought has been serviced with 5w-30 synblend according to the receipts from the police department from 0 to 150k miles when they sold it. I bought it with 165k or so. I plan to use 0w-30 - you think that'll be ok? I know you're talking about a 3v and I'm talking about a 2v but I'm just curious.


If it were my Crown Vic I'd run 10W30 in it.



It's still a 30 grade.