High viscosity causing worn rings?

[moribundman]

What would you tell someone who's convinced that a 15W-50 oil has caused collapsed rings and increased oil consumption? He think that the thick oil increased compression and resulted in more blowby. He didn't say why he thought wear increased.

 

[Quest]

My experience with higher viscosity oil causing pumping problems (when cold) and the delayed lubrication on the cylinder wall caused severe scuffing.

Not aware of anything assoicated with ring collapse. Have him check his cylinder wall for scuffing instead. Most likely the scuffing (fine grooves) leads to excessive blowby.

 

[pitzel]

Oil must slip past the rings to a small extent to lubricate them in their entirety. If the oil is so 'thick' as to not permit this slippage, of course there will be some accelerated wear of the rings themselves.

They say with respect to aviation engines that 'no-consumption' is actually a problematic condition as the engine itself requires some consumption for proper lubrication throughout. I am sure the same logic can be applied to a petrol engine in an automotive application.

 

[FowVay]

quote:

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Originally posted by moribundman:
He thinks that the thick oil increased compression and resulted in more blowby.

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Hmmm, now this is a different way of reasoning I suppose. The compression is increased because of less blow-by, a result of the thicker oil. Yet the increased compression has resulted in more blow-by??

So what really did come first,, the chicken or the egg?

 

[moribundman]

quote:

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My experience with higher viscosity oil causing pumping problems (when cold) and the delayed lubrication on the cylinder wall caused severe scuffing

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quote:

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Oil must slip past the rings to a small extent to lubricate them in their entirety. If the oil is so 'thick' as to not permit this slippage, of course there will be some accelerated wear of the rings themselves.

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I doubt this would ever occur with full synthetic 15W-50 in southern CA with its very mild to warm temperatures.

quote:

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Hmmm, now this is a different way of reasoning I suppose. The compression is increased because of less blow-by, a result of the thicker oil. Yet the increased compression has resulted in more blow-by??

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Maybe he thinks compression increases temporarily until the oil gets blown by the rings? He doesn't elaborate.

I'm inclined to dismiss the claim of 15W-50 oil resulting in collapsed rings, especially in a mild climate.

 

[haley10]

I can't see M1 15W-50 being a problem at all. It must be more like what HiRev said. It's not stock and may have something to do with the tuning. The oil is not the culprit, imho.

A properly interpreted UOA is in order. Who did the tuning and to what extent?

 

[Sam3]

I tryed to find the BITOG thread, I think it was posted by Blue99? Anyway, When I read the link I said to myself, "AEHass is right"

http://www.iantaylor.org.uk/papers.htm
Looks to be some interesting articals here.

http://www.iantaylor.org.uk/papers/Additives2001.pdf
page 18 of 36.
How can lower viscosity lubricants give thicker
top ring oil films ?

Lessons from ring-pack modelling and
measurements
• Reverse blowby correlates with oil consumption due
to transport of oil mist
• Detailed ring motion has big influence on where
deposits form, and lubricant motion within ring-pack
• Ring motion determines the residence time of the
lubricant in the ring-pack : important for lubricant
degradation and deposit formation
• When rings are tilted, blowby to the sump is increased
• The lubricant formulation can affect ring motion


Check out the graphs on pages 13 and 18.

[ May 30, 2005, 02:27 PM: Message edited by: Sam3 ]

 

[Hirev]

quote:

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Originally posted by moribundman:
This is about a ca 1995-1997 Audi 2.8 12 valve motor with ca 150k miles on the clock. The motor has been tuned to put out considerably more hp than stock (172 hp). He also mentioned that the rod bearings were in less than good shape.

RayH, Audi recommends viscosities from 5W-30 to 20W-50/10W-60 in this engine, depending on ambient temps and type of oil. I believe he used M1 15W-50.

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When rod bearing clearance starts to become excessive they flow much more oil out. Bearing clearances more or less controls internal bleeding. The result is more oil ends up on the cylinder walls. Than it becomes a battle for the ring package to deal with the excess oil on the cylinder wall. Rings with 150K miles on them are going to fight a losing battle. As they are not in the best of shape to fight a battle like this.

Don't know how hard this motor has been ran but it sounds like it could be getting tired.

He also may want to replace his PCV valve to see if it helps. They are cheap and can cause a motor to use excessive oil. They are often over looked by the average motorist.

A leak down test, UOA, and Terry's Services might will be worth while.

I have used Mobil 1 15w 50 in many different applications from drag racing cars, 454 jet drive boats, and motorcycles. Never had any issues with this oil.

I wouldn't have the Grape Nuts to try a thin oil on a motor with "rod bearings were in less than good shape" as some are suggesting here.

[ May 30, 2005, 02:36 PM: Message edited by: Hirev ]

 

[the_oil_dealer]

quote:

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Originally posted by Sam3:
http://www.iantaylor.org.uk/papers/Additives2001.pdf
page 18 of 36.
How can lower viscosity lubricants give thicker
top ring oil films ?

Lessons from ring-pack modelling and
measurements
• Reverse blowby correlates with oil consumption due
to transport of oil mist
• Detailed ring motion has big influence on where
deposits form, and lubricant motion within ring-pack
• Ring motion determines the residence time of the
lubricant in the ring-pack : important for lubricant
degradation and deposit formation
• When rings are tilted, blowby to the sump is increased
• The lubricant formulation can affect ring motion


Check out the graphs on pages 13 and 18.

---

very basic concepts, worded to sound intimidating. I can think of much more influential factors than viscosity that would cause 'ring "tilting"' and damage. For instance piston to bore clearance, rod to stroke ratio, piston and bore metalurgy, operating condition/temperature, oil pressure, piston loading... and we're pointing the finger at a synthetic 50wt???? you have got to be joking!! I just cannot take this seriously.....

Most modern engines have under-piston oil squirters which would totally negate "oil misting" concerns. Even if this engine relied on splash for cylinder lube, which is a stupid design, then a 50wt would actually excel in this regard, providing a more robust film that does not wash away as easily.

Other factors to consider are hone cut depth and angle, piston sidewall loading (r/s ratio, stroke length) which all play a far more involved role in ring tilting and movement. If your buddy is getting more CONSUMPTION with a thicker oil, it indicates poor ring tension, not to mention any oil getting upward into the combustion chamber is certainly reducing upper ring wear dramatically. In conclusion, M1 15w-50, will not wear your rings out, period.

 

[Sam3]

"I can think of much more influential factors than viscosity that would cause 'ring "tilting"' and damage."

HEY I agree!

Below is from my second post
"Carbon Knock" in modern engines did not occur even at high mileages in Japan. When these same engines were sold in the US, customers began objecting to the engine noise after only a few thousand miles in some cases. Some customers required replacement of the cylinder heads because of the damage caused by the piston hitting the deposits. Other customers switched brands of gasoline or used after-market deposit control additives to help remove deposits causing carbon knock.
The problem in the US was attributed to high-additive treat rates being used for IVD control.

cut&paste from:
http://www.enginemanufacturers.org/info/guidelines/3c04WWFuelchart

Somewhere I got another Link to go with this one.

 

[moribundman]

quote:

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He also may want to replace his PCV valve to see if it helps. They are cheap and can cause a motor to use excessive oil. They are often over looked by the average motorist.

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The 12v engine doesn't have a PCV valve.

Anyway, his engine has been rebuilt over the past 8 months or so. The pistons were modified for gapless rings and he has had some other things done, I believe. The people who have been rebuilding his engine are Audi specialists. They attributed the collpased rings to the underiszed low-tension rings. However, I know of plenty 12 v engines that have at 200k miles still compression within factory specs. I would think his excessive wear was due to his engine mods and not oil-related. As far as I know, the engine is going to be installed today, so I'm sure I'll soon get word regarding how it's running.

 

[Sam3]

"Most modern engines have under-piston oil squirters which would totally negate "oil misting" concerns."

NO NO NO no. The Oil Misting is the oil flow through the ring pack, (I think)

See:
About page 19, How ring gap affects oil flow through the ring pack.
http://www.iantaylor.org.uk/papers/Additives2001.pdf

edit to say:
You Can gap the rings to minimize the amount of time, that the pressure between rings 1 and 2 is greaterthan the cylinder pressure.

edit again;
But? Hmmm? What would be the optimal flow in the ring pack?

[ May 30, 2005, 05:06 PM: Message edited by: Sam3 ]

 

[JohnBrowning]

I would ask him if his docter had recently changed or lowered his medications? Then I would ask him how long he has been diloutional! He can send all of his used 15W50 my way!! Just make sure he pays for shiping!!

First you can not collapse a ring! You can wear one out through neglect, cheap oil, over heating engine, sustained high speeds, total number of miles of piston travle etc.....15W50 is not going to casue scuffing either. Now if you were dumb enough to use it dureing a Michigan or Canadian winter then yes it could casue some issues! Mobil-1 sells millions of gallons of 15W50 or Walmart would not cary it in the 5 quart jug! Walmart only keeps movers on the shelf! What about the billions of gallons of 20W50 sold each year buy all major oil bottlers? What about the trillions of gallons of 15W40 sold globaly per year for commerical use?

See if he can put his head in a vise while lighting up a light bulb with his mouth!! I am glad I am not a Tech. or service writter because I hate dealing with people when it comes to cars!!

What is next his cigeret lighter blew a gasket becasue his 75W90 gear lube is too thick?

See of you can sell him blinker fluid!!!!

 

[moribundman]

I know, I know, the following has nothing to do why the rings clapped out. I just thought some people might like to see that motor.

Disassembled motor:
http://forums.audiworld.com/12v/msgs/45131.phtml

Assembled motor
http://forums.audiworld.com/12v/msgs/46831.phtml
The post also talks about the setup.

 

[Nosmo King]

I have a bore scope and I have seen two VW water cooled motors that clearly had the cross hatch still visible on the bores after the motor had done just under 100,000 kms. Both these motors were made in the eighties and ran 20w-50 dino oil year round.

I have also seen bores worn out in about the same mileage. The worn out bores were caused by the young owners using CAI ( cold air induction )and those dreadful K&N style gauze filters.

 

[JohnBrowning]

His modifications and driveing style are surely what lead to ring failure!!!! THe guy even wore out his transmission! I have never worn out an engine or transmission in a non-race vechile! I wounder what he will blame the next ring failure on? He obviously can not take credit for wearing his motor out!

 

[Dart-Swinger]

What's he blaming the warped head on that caused the head gasket failure and had to have one of the heads shaved?

Sounds like he was running the **** out of the motor and that's what caused his problems.

 

[yannis]

quote:

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Originally posted by FowVay:
So what really did come first,, the chicken or the egg?

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This question has been answered...the egg made the chicken ,the snake egg. We are all snakes

 

[Hirev]

quote:

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Originally posted by moribundman:
What would you tell someone who's convinced that a 15W-50 oil has caused collapsed rings and increased oil consumption? He think that the thick oil increased compression and resulted in more blowby. He didn't say why he thought wear increased.

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How muck oil consumption? How many miles on this motor. And what motor are we talking about.
I have rebuild many motors and I don't understand the use of the words collapsed rings here. Is he talking about stuck rings? Usually the result of poor past maintenance or overheating. Or could he be talking about rings that have lost much of their tension? If so overheating is the cause of this.

 

[Ray H]

I'd go along with the proposal that poor pumpability at cold start-up (yes, even in So-Cal) would accelerate wear of the rings and cylinder walls. Particularly so if the car was driven much in short start-stop cycles and/or city traffic. There could also be other issues at work, too - fuel and/or coolant contamination of the motor oil. If the owner tends to be lax about timely, routine maintenance, that wouldn't help either. (Gahhh! What OEM recommends 15W-50 grade for normal driving?!

)