thick and thin and perspective

[427Z06]

Bar1, you going to give us more details on the VW approved longlife diesel oil used, or you going to leave us in suspense?

Seriously, what are those pictures meant to imply?
Or are they just meant to entertain those who have never seen worn out internal engine parts?

 

[427Z06]

quote:

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Originally posted by JAG:
Another is the property of oils in which they increase in viscosity as the pressure on them rises very high (Newtonian vs non-Newtonian fluid).

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Good point JAG. Most people go no further than where kinematic viscosity and temperature determine grade and the other lubrication regimes are barely discussed.

 

[bar1]

427Z06:
I'll ask the owner for details regarding oil.
I found these photos and the informationat the Norwegian VW/Audi club forum.

Just entertaining

I've never seen a diesel engine that worn out after such short mileage.
The marks on the "arms" are almost 0.035 inch.

 

[bar1]

427Z06: Owner didn't know. Dealer oil probably Castrol or Shell in recommended visc. and with VW longlife spec.. It's not the oils fault.
2.5 TDi V6 with engine codes AFB - AKN - AKE - AYM all have this problem.
Work is done as "extended warranty" paid by dealer/Audi.

 

[Hirev]

So what is your thoughts on this as posted by MolaKule from this post? Link to MolaKule postings

"1. The temperature for an HTHS measurement is done at 150C or 302 F, which is the average peak temperature likely to be encountered in a bearing.

2. The oil is mechanically sheared at a rate of 1 x10^6 shearing operations/second.

3. Minimum Oil Film Thickness measurements (MOFT) of operating engines did not correleate well with actual wear in service. A method was devised by which the oil temperature would be elevated to worst case and sheared to determine the optimum viscosity which better correlated with wear.

Three Exxon Researchers found that a minimum HTHS of about 2.8 mPA.s was the MINIMUM HTHS viscosity needed for normal wear, with the higher the HTHS being better for minimum wear. IN general, the higher the viscosity, the greater the HTHS.

For example, in a fleet of taxicabs using a GM 4.3L V6 engine, if the HTHS was 2.35, the startup film was 0.097um and 2.56 um at running; if the HTHS was 2.98, cP, the Startup oil film thickness was 1.231 um while the running film thickness was 3.22 um.

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.

I should also mention that this test showed little differences in wear between a high quality 5W20 and a 10W30 for oils of close HTHS. For example, The average wear of one of the 3.8L V6's showed a total wear of the Connecting Rod bearings as 48.4 grams for the 5W20 verses 44.3 grams for the 10W30. For a 10W40 oil, the wear was 39 grams!!!

[Mola's comment: I think this test verifies my earlier comments that most daily driver engines can use any oil from a high quality 5W20 to a 15W40 fleet oil.]

Summary: It was found that HTHS correlates better with wear values found in actual oil analysis and actual tear-down measurements than does measuring the oil film thickness in situ."

 

[GMorg]

Thanks Hirev,

I had not seen that thread.

 

[Titan]

GMorg, I THINK you might be able to plot at least FOUR curves without getting ridiculous. A cold and an operating temperature curve for Upper (valvetrain) and Lower (bearings) engine wear. That way, if you rarely get to operating temp, you could select a oil that most nearly fits the two cold curves, or if you always run it hot, you could concentrate on an oil that meets the hotter curves better.

 

[moribundman]

quote:

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Bar1, you going to give us more details on the VW approved longlife diesel oil used, or you going to leave us in suspense? [Big Grin]

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Since it's a 2001 Allroad using LL oil in a diesel engine, the proper oil is either VW 506.00 (non PD engine) or VW 506.01 (PD engine). Both oils are low HTHS oils (>/=2.9 to <3.4).

 

[427Z06]

Hirev, yes I've read and even posted on that thread.

I'll just make a few short points.

First, 2.1 HTHS would correlate to about a 0w10 (although in reality it is just not defined in the J300 spec). I'm not aware of any manufacturer that recommends a 0w10.

Second, the test was performed on 4.3L Taxis. The 4.3L is 3/4 of a Gen. I Small Block Chevy (SBC). GM has long recommended Xw30s in those engines. Likewise, most SBC enthusiasts won't put anything less than Xw30 in their engines. And if they blueprint them with clearances on the high side, they'll even run Xw40s and sometimes Xw50s. Although I'm not as quite as familiar with them, I bet similar comments could be made for the Buick 3.8L.

Finally, that study was from around 1995? Taxis generally run all day long, so the engines mainly see temps at the upper range. And we don't have all the details of the test, such as was it run in Las Vegas or New York in the middle of summer? What were the range and average oil temps? What were the percentages of idling, stop&go, highway use, etc?

 

[427Z06]

OK, allow me one more point.

To see that amount wear out of the bearings on the dyno run, the temperatures must of been highly elevated and/or run for a looong amount of time.

 

[moribundman]

Most bearing failures, unless I'm mistaken, occur due to oil contamination, for example when abrasive particles get embedded in a bearing cap.

What about ring and cylinder wear? Here we got very high temperatures and forces on the oil film. We also do not have full hydrodynamic lubrication at all times. What viscosity ensures optimum life of cylinder finshes and rings?

Reducing blowby must be on the agenda, especially with optimized emissions control. What's the correlation between amount of blowby and viscosity?

What about low-friction coatings and plating on rings? How fast do these coatings wear off, and what then?

 

[427Z06]

Good point, mori. I believe Titan is thinking along the same lines. There's at least three engine areas of consideration as this graph depicts.

 

[Hirev]

quote:

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Originally posted by moribundman:
Most bearing failures, unless I'm mistaken, occur due to oil contamination, for example when abrasive particles get embedded in a bearing cap.

What about ring and cylinder wear? Here we got very high temperatures and forces on the oil film. We also do not have full hydrodynamic lubrication at all times. What viscosity ensures optimum life of cylinder finshes and rings?

---

When I worked at an automotive remanufacture facility in the early 80s for a couple years. One problem that stood out. With very few exceptions the cylinders closest to the water pump inlet nearly always had much more taper in the cylinder bores than the rest of the cylinders. The short trippers (especially with cooler thermostats) could get down right ugly. To the point that a .030 overbore would not clean up the front cylinders.

I always suspected thermodynamics play a major role in cylinder wear after working there. I seen many examples of 160 deg thermostats and occasionally no thermostats killing an engine early.

Back than it seemed like valve guides and valve train and valve seal were the 1st problems to appear on a motor going down hill. We also seen a fair amount with bearing knock or actual spun bearings especially out of pickups.

 

[hominid7]

In reading data specs on oils, it seems nowadays that most dino 5w30's and 10w30's are almost the same. I guess 5w30's got a tad more robust to meet the GF-4 standards and 10w30's got a little less robust to meet the EC spec.

I guess the real argument however is to use or not to use 5w20.

My car seems to like 5w30 in the winter and 10w30 in the summer, which is also what my owners manual recommends, so that's what i'm sticking with

 

[1sttruck]

Another perspective is that a number of clearances in a wide range of internal combustion engines are determined by thermal properties of engine materials. This is why as we've seen from some posts that there isn't that much difference in bearing clearances, although one could assume that highly loaded, older design air cooled aircraft engines would might be set up with larger clearances, where a 50 weight seems common, compared to a small water cooled engine used in a narrow operating range, where 30 weights seem more common. In the middle might be water cooled engines used under high loads, like cars designed for extended speeds in Europe, where heavier oils seem more common than lighter oils. Sump size and drain intervals are also a consideration, where lighter oils with less margin would need more frequent changes, although it seems that the oil change intervals in places like Europe are often 'over the top' even with their heavier oils, due to a different set of marketing pressures.

In general though maker recommendations seem to be safe thse days for almost everyone, whether it's 5w20 or 5w40. Some want better fuel economy and can probably use lighter oils with little concern, it is prudent to see how others have fared, and heavier oils (with adequate cold temp start performance) will tend to provide better wear protection, at the expense of power loss and fuel economy.

Note that maximum engine is one of the most boring peformance parameters, considering that it typically means living with a beater for a bit longer.

 

[Gary Allan]

This isn't quite white paper material here ...but I figured I'll throw a shovel full or two into the furnace here.

They travel light - but they're not from KAPAX

Because these engines run hotter with tighter tolerances, they have deep sump pans that hold nearly seven quarts of oil. Oil viscosities run much lower than we are used to with vintage Ford V-8s--5W20. Running anything heavier isn't healthy for the Modular V-8 because of its tight tolerances. The lower viscosity oil also creates less internal friction, which frees up power and improves efficiency.

 

[427Z06]

Hirev, I recall a similar conversation with a gent that worked in an engine overhaul facility, only he rebuilt mainly SBCs. He noted that bearing wear generally increased as you went from the rear of the engine, where the main gallery is first fed, to the front of the engine. The further north the engine came from, the more pronounced the effect.

 

[1sttruck]

The original factory fill seemed to be Mobil 1 15W50.

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[427Z06]

Different pistons, rings, bearings, clearances, etc. But what the heck, we all know the engineers don't have the same superior knowledge as some BITOG lubrication specialist.

 

[bruce381]

quote:

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Originally posted by 427Z06:
Good point, mori. I believe Titan is thinking along the same lines. There's at least three engine areas of consideration as this graph depicts.

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Where did this graph come from?
I do not agree that EHD lubrication takes place much in a modern engine let alone the rings, also lowest friction would be in the HDL range not the EHD range since EHD is basicly a sold lube at that point friction will rise.
bruce