"Engine oil viscosity has VIRTUALLY NO EFFECT ON WEAR."

[wulimaster]

quote:

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Originally posted by Ugly3:
]The problem I have is that I have not seen any data that suggests the wear metals in a used oil analysis relate in any way to actual engine wear. Look at the Paradise Garage study, there is virtually no wear reported in the 1000 mile used oil analysis from 5,000 miles to 15,000 miles. I don't think that can be so I think there must be some anomoly going on.

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If you just look at the numbers between 1k and 12k you will get a better idea of the wear.

I noticed that comparing the Amsoil 3.5HTHS to the Mobil 1 3.08HTHS wear numbers it shows that over the 11k period between 1k and 12k the Amsoil has about 1/2 to 1/3 the wear on the iron/lead/copper/aluminum.

I wonder if this difference is due to the HTHS difference?

 

[moribundman]

quote:

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I wonder if this difference is due to the HTHS difference?

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Am I the only one who thinks that some car makers specify oil to have a minimum HTHS viscosity FOR A PRETTY GOOD REASON?

 

[buster]

I'd say NO bc the oil didn't shear and a higher HT/HS implies that thicker is better and I don't believe that. M1R = 10cSt.

 

[moribundman]

quote:

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A jump in HTHS by about +1.5 results in approximately 1/5 the wear. Now this relationship is not linear and flattens as one nears a 40+ weight oil.

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Sounds to me like an XW-40 offers the best compromise between low wear and good flow.

 

[XS650]

quote:

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Originally posted by LarryL:
I have an '84 Honda Civic wagon that has 375k miles and the engine has never been apart or the head removed. ...I'm getting a bet nervous waiting for something to happen... there's no place to go, anymore, with the viscosity.

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Report back in a couple of decades and let us know how it's going

You can afford to let it get 3 or 4 times as bad on oil consumption before you need to declare it a problem. If it was a new car under warranty it would have to be 5 to 10 times as bad on oil consumption before the manufacturer would even discuss warranty with you.

I think you would have been just as well served to let oil consumption go up to the 3k or so miles/qt before going to thicker oil instead of keeping oil consumption at it's present level.

You're the one with 375k miles on your engine though, so I bow in your general direction.

Please post your approach to maint and driving for long engine life in one of the general threads. A lot of of us could learn somthing from you.

 

[ToyotaNSaturn]

Larry, down in Australia, they sell 70wt oils, you have a ways to go before you should become worried.

Oil consumption? Give Auto-Rx a try with 2 treatments. I swear it's the best stuff ever made. Well, except for an ice-cold Fosters.

It's amazing to hear the stories of how a well maintained car can last a good long time. Like XS said, please do share with us your maintenance habits...

 

[haley10]

quote:

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Originally posted by ToyotaNSaturn:
Larry, down in Australia, they sell 70wt oils, you have a ways to go before you should become worried.

Oil consumption? Give Auto-Rx a try with 2 treatments. I swear it's the best stuff ever made. Well, except for an ice-cold Fosters.

It's amazing to hear the stories of how a well maintained car can last a good long time. Like XS said, please do share with us your maintenance habits...

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Agree 100%. I would try two (2) ARX or similar before assuming that a bump in viscosity is necessary.

 

[Dr. T]

quote:

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Thinner oils outperform thicker oils in some ways because these additives are actually doing something. They do not come into actual use in thicker oils. Thicker oil does not lubricate as well as a thin film of these additives. I will stop here as this is a huge SAE topic.

Thicker oils have more problems with oxidation and breakdown. If a lubricant moves through a bearing at half the speed it gets hotter before exiting the journal. A thinner, faster moving oil cools the surface better and also heats up itself to a lesser degree. It therefore thins less than a thicker oil. This is one reason why thicker is not necessarily better.

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[/QB][/QUOTE]

Where is this quote from? Does it mean that addatives in thicker oils don't work?? That's balony. Thicker oil does not lubricate as well as a thin film? We'd all be using WD-40 if this were true. Thicker oils have more problems with breakdown and oxdiation? Right...that's why BMW went to a 0-20 from the 5-30....it was TOO thick to properly protect

Both of these paragraphs are nonsense. The oil heats up from the heat generated from combustion. The cooling systems job is to keep the engine cool. The oil does some cooling as a secondary function. The oil getting hot (from stress of combustion) is the the primary reason for breakdown. Thinner oils cannot resist this as well as thicker base oils as a general rule of thumb.

 

[Motorbike]

Proof is most often found in tear down .

From another site concerning a 70's model V-8 ran on 15w40 for many a year :

I took a few rod / pistons out. It appears the rod bearings are wore through the first layer in a very small area on one side

Thats abbreviated and I take it to mean the trailing edge all the way round the diameter , he went on to tell how the rest of the same bearings looked good other than the noted section. I might add , that not from elongation of the big end of the rod from hi-rpm stress but ....

Please read the post by cit1991 and see if it starts making sense what happened to this motor or if it helps this thread .

Film Strength Thread

 

[LarryL]

XS650, part of the approach is to live in Southern California. This car has never seen snow or ice and very little rain. And you are right there are things you can do to make a car last longer. The cylinders look like new and the valves seldom require much adjusting. This car has convinced friends that synthetic oil is worth the trouble. Some need something to look at, specs and reports don't work for everyone.

 

[ekpolk]

quote:

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Originally posted by LarryL:
I have an '84 Honda Civic wagon that has 375k miles and the engine has never been apart or the head removed. In those years I've gone from 5w30 dyno to 5w30 synthetic to 10w30 to 10w-40 to 15w-50 and now 20w-50. These jumps have been paced by oil consumption between oil changes, which is about a half quart per 5k miles, a rate that has been pretty constant for 20 years. The compression is at factory new specs and with in a few pounds from highest to lowest (208, 205, 209, 205). My only reason for steping up the viscosity was to control oil consumption. I'm getting a bet nervous waiting for something to happen... there's no place to go, anymore, with the viscosity.

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You still have room to move. Next, you can try a 60 wt racing oil. . .

How has the mpg moved, if at all, with these changes?

I though we buried this rotting corpse back last April

.

 

[ekpolk]

quote:

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Originally posted by Dr. T:
{snip}
The cooling systems job is to keep the engine cool. The oil does some cooling as a secondary function. The oil getting hot (from stress of combustion) is the the primary reason for breakdown. {snip}

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I would slightly disagree with this. Below the coolant jackets, oil is the only coolant available. Basically, the crankshaft, bearings, etc. are totally dependent upon oil for heat removal.

 

[JohnBrowning]

berg, Fairly common knoldge that HTHS not SAE viscosity rateing is what determines wear rates. Their is also some additive package at work as well.

What does it matter what a race car(s) is running in Austraila as an oil? Last I checked very few of the Bobietheoilguy crowd were too awfuly worried about their race car! It a safe bet taht most of use are not worried about biasing toward HP at all cost! I usualy do not tear down and rebuil my engines until they have 300,000 miles on them.

I understand the point you are trying to make but the information you are useing has no correlation to our daily drivers. light weight oils have been used for qualify in most forms of raceing in the USA. Tradionaly a thicker oil went in after qualifying. We are seeing more and more teams switch from 20W50 to 0W30 and such. The usage cycle and maintence schedule though has no implactions for most of us.

P.S. I was reading an article in own of my car magazines. It was about the Army's drag car. They use a 70Wt oil in the crank case then add extra thickners to that. I am not about to go out tomorrow and put 70Wt in my Camry and add a bottle of thickners to that!

 

[buster]

quote:

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Fairly common knoldge that HTHS not SAE viscosity rateing is what determines wear rates. Their is also some additive package at work as well.

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I don't agree John. I don't think Higher HT/HS gives ANY indication of wear. If that were the case, the 20wts and Mobil 1 would be worse then the other oils. Not so. For the 1,000,000 time, viscosity is just one aspect of an oil.

 

[JohnBrowning]

buster, You are not paying attention!!!! HTHS is not linear with SAE Viscosity!!!! You can have a nice HTHS with a SAE 20Wt oil and a poor HTHS with a SAE 30Wt oil!!!

HTHS and wear rates is not an opion it is a scientificly proven fact! The research can be dublicted and has been by more then one company.

The following is fact not opion:


HTHS AND BEARING WEAR
In Dynomometer wear tests using four GM 3.8L engines, the wear mass of a connecting rod bearing was as follows:


HTHS 2.1
mass loss (gm.) - 190

HTHS 3.2
mass loss (gm.) - 28

For "mains" bearings:

HTHS 2.1
mass loss (gm.) - 150
HTHS 3.2
mass loss (gm.) - 40

A jump in HTHS by about +1.5 results in approximately 1/5 the wear. Now this relationship is not linear and flattens as one nears a 40+ weight oil.

Notice that no place in this information is SAE viscosity rateing given!

Now what minimum HTHS is required for each individual engine is a different story all together. Their are plenty of common elements though that can be gleamed from this study and that is that wear is dependent on HTHS! Each car will have a minimum and exceeding the minimum by 1.5% can reduce wear to 1/5 the rate of the minimum HTHS for that engine.

The design of the engine and the usage and duty cycle will ultimately determine what the minimum is for each application.

This was determined by weighting each bearing on an analytical scale. You might recall these from chemistry or physiology class. Then the engine is assembled and ran for prescribed duty cycle. Then they tear the engine apart and re-weight the parts, visualy inspect and rate the parts etc... This is far more precise then UOA. I do not think anyone has calculated the bearing mass worn away based on PPM of wear metals in the oil and crank case volume as of yet.

We also can not tell wear the bearing wear is occureing in the engine with UOA. If we see 20PPM of lead, 5 PPM of tin, 40 PPM copper we know that their is wearing wear but from where? Is the rod bearings,cam bearings, main bearing, oil pump bearings etc.... It could be just one of them or all of them. Rod bearing almost always take a harder hit then the rest of them and are not as tolerant to loss of material! SO it is important to know where this loss is comeing from and UOA will not tell you definatively.

You will also note that M1's lowest HTHS I belive is 2.99 witch is awfuly close to the studys positive refernce HTHS of 3.2 wich reduced wear to 1/5 that of the lower 2.1 HTHS oil.

 

[Jerry]

Posted this awhile ago. Looks at ultra low viscosity for auto use.

http://www.pecj.or.jp/gijutu-report/e-report/01M445e.pdf

CUL
JR

 

[Ken2]

Generally speaking you pick an oil viscosity to relate to the size of the bearing clearances. Bigger clearances require thicker oil & vice versa. Also important is the size of the bearings vs. the load on them. Larger bearing surfaces for the same load can use a ligher vis oil. All of this, plus oil passage size, etc., etc., are what the engine designer looks at when he chooses an oil for an engine.

I also feel that HT/HS viscosity is important regarding wear, but modern additive packages have reduced that importance somewhat.


Ken

 

[buster]

I think Ken hit the nail on the head and was getting at what I meant to say.

quote:

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Generally speaking you pick an oil viscosity to relate to the size of the bearing clearances. Bigger clearances require thicker oil & vice versa. Also important is the size of the bearings vs. the load on them. Larger bearing surfaces for the same load can use a ligher vis oil. All of this, plus oil passage size, etc., etc., are what the engine designer looks at when he chooses an oil for an engine.

I also feel that HT/HS viscosity is important regarding wear, but modern additive packages have reduced that importance somewhat.

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Jerry, thanks for that link. I found it interesting that lowering P in the oil resulted in improved fuel efficiency.

[ January 20, 2005, 10:40 PM: Message edited by: buster ]

 

[LarryL]

ekpolk, the mileage has been pretty constant at 37mpg. I was getting a little higher but about 10 or so years ago they re-formulated the gas. Before it was 39mpg. And about going up in viscosity, I think I'm going to run a little longer with the current 20w-50 and accept any increase in consumpion. I just posted this information because the only reason I went up in viscosity was overall engine wear and it has kept the consumption really constant. So I think engine wear should be considered when picking an oil viscosity. The only major repair has been the replacement of the camshaft. One lobe started to wear, it lost its surface hardness. The other lobes were worn but fine and withing spec. If I have to ever do a valve job I'll post pictures.

 

[JohnBrowning]

buster, You must be trying to push my buttons or your speed reading course is falling you!!! Slow down and read what I am typeing! You keep talking viscosity and I am not!!! We are obviously haveing too entirely different conversation on unrelated subject matter!

You have some hang up on viscosity and thick v.s. thin but that is not what I am talking about!

I am talking HTHS not SAE viscosity. You can have a 20Wt with an HTHS of 3.3 and a 30Wt with an HTHS of 2.9 or less. So again you need to get this idea of SAE viscosity out of the conversation!!! Now while it is true that with conventional oil HTHS is preety linear. Once we move over to synthetics the amount of linearaity of HTHS based on viscosity goes out the window!

HTHS is one of the reason that GC does so well! IT is not the viscosity so much it's HTHS. I am pretty sure we will find out it gets it's HTHS from a diester or TPE base stock. HDEO get their HTHS from the heavy base stock. Redline gets it's HTHS from the exotic TPE and TPO base stock it uses. So while you can arive at a nice HTHS of 3.5 or higher from either useing exotic base stocks or increseing viscosity it does not matter! The HTHS is all that counts! Additive packages help but they are secondary AW agents. The additive package only helps when the base stock fails. The HTHS provided by GC's base stocks is what allows this oil to do so well in so many different vechiles in spite of it's weak additive package. Schaffers does well too and they do not use alot of additives. Synergen does well and they do not use a lot of additives either.