How should we use/interpret UOA's?

[RPMster]

From the time I started following threads on BITOG years ago, before even becoming a member here, I always thought UOA's were supposed to be used as a very basic tool: To identify current engine problems, or problems that are starting to form, and to give us a general ballpark idea of when we should change our oil.

When using TBN/TAN and wear metals to determine how long an oil can be pushed in a given application, how conclusive is that data, really?

If we push an oil to its absolute limits every OCI going by the data, and the numbers look good after a series of UOA's, do we have enough conclusive evidence that 200,000+ miles of doing this won't have any negative effects on the engine?

In other words, are there long term effects that won't show up immediately after a few UOA's?

Theoretical example:

- Two neighbors have the same exact vehicle
- They work in the same business park, same commute every day
- Same driving habits
- Use the same oil
- AND, for the sake of this example:

*** Engine components and all accessories for these 2 engines were manufactured to absolutely identical specs down to quantum measurements (internal engine clearances/tolerances, pistons/rings, oil pump, water pump, radiator, valvetrain pieces, etc).
*** Also, all variables remain "like new" for both engines, such as PCV condition, cooling system condition, etc.

At 50,000 miles, both drivers decide to start doing UOA's and changing their oil based on TBN/TAN and wear numbers.

Driver A decides to change his oil when his UOA's say TBN and TAN are both at 1.5 (just an example)

Driver B decides to change his oil when his UOA's say TBN is at 1.0 and TAN is at 1.9 (again, this is just an example)

After a few UOA's, both engines appear to be in great shape, going by the wear numbers. Driver B, who does longer OCI's (1.0 TBN / 1.9 TAN), has wear numbers that are trending appropriately with mileage.

Both drivers intend to keep their vehicles for over 200,000 miles.

So......

Going by the data from a few UOA's, and assuming both drivers continue with their elected oil changing routines, can we conclude that both engines will be in the same shape after more than 200,000 miles?

 

[gman2304]

Yes.

 

[HTSS_TR]

No. Driver A's engine will be in better shape than Driver A after 200+k miles. When TBN is near 1.0 or lower it doesn't protect engine as well as when it's at 1.5 or higher

 

[RPMster]

This thread was meant to invoke thoughtful conversation. When responding, please try to expand on your ideas rather than only giving a simple "yes" or "no" answer. Thanks in advance.

EDIT:

Let me add this to the end of my original post:

Going by the data from a few UOA's, and assuming both drivers continue with their elected oil changing routines, can we conclude that both engines will be in the same shape after more than 200,000 miles?

If your answer to this question is "yes" or "no" then how did you come to your conclusion?

 

[edhackett]

No. The wear particles shown in a simple $20 UOA only show a subset of the wear, not he total wear that is taking place. The same $20 UOA does not give any any indication of varnish or sludge formation. More sophisticated testing, plus visual inspection would be required.

Ed

 

[901Memphis]

Wear metals can level off further into the OCI. You might register 20 ppm iron for the first 5k miles then only 2ppm each thousand after just as an example throwing numbers around. The information was from an SAE paper. I think DNEWTON has the link.

 

[OVERKILL]

Both Doug Hillary and Dave Newton have some good articles on the front page of this site on this topic.

Basically, your initial premise is close to correct: UOA's are used to determine proper OCI length through contamination (wear metals, insolubles, fuel....etc) and the rise of TAN, reduction in TBN. As well as a potential indicator of mechanical issues through the possible spikes in various metals (lead, copper....etc), indicate an intake tract leak (silicon increase) and check for coolant or water ingress.

They are not for "tracking wear"; Comparing the performance of different oils to each other, as each lubricant will have its own "signature" in terms of metals and this does not directly correlate with wear.

 

[fdcg27]

There are other factors to consider here.
Oxidation and shearing need to be considered as well.
Without regard to TBN or TAN, if driver B sees considerably more oxidation in his samples than does driver A, he may be on the way to heavy engine deposits which will not show up in any UOA.
If driver B sees thicker oil after his higher mile drains than does driver A, that is surely a clue that the oil is excessively oxidized for the mile he's run it, without regard to the rest of the UOA results.
Do wear metals in a UOA mean anything?
I think they do, in that they are at least a surrogate for overall engine wear.
As Dave Newton has pointed out, though, it's rate per thousand miles run that matters, not the gross numbers.

 

[victorkoga]

according to your scenario In the long run the difference between driver a and b will be minuscule. Now if you told me that driver b often forgets to get his oil changed , neglects basic maintenance and drives around for thousands of miles with oil a quart low then i would say at driver b isnt going to see 200k miles.

I personally think a uoa is a useful tool if you are extending your oci beyond the manufacturers intended oil service, but the agonizing over 10 ppm of iron doesnt translate into real world engine health . I am going to guess that if you are getting a uoa done or you even know what a uoa is then you take pretty good care of your car and 90% of the time that is all it takes.

I am a ase master tech who works for my local sheriff dept. We have all of the current marked cars offered by the big three except for the caprice (the impala has burned gms rep with our boss) . we run impalas with a 4 quart oil capacity 3.9 v6 ohv 4000 miles and god knows how many idle hours on a conventional oil . The chargers (v8) and crown vic (v8) get mc 5w20 synblend get the same treatment. We have never had a internal engine failure . No sludging no spun rod bearings nothing.

i imagine if i had a uoa done on those police cars it wouldnt be pretty . That is the split between a lab test and reality . Uoa are great for telling you the condition of a oil , but terrible for telling you the condition of your engine .

 

[RPMster]

Originally Posted By: OVERKILL
Both Doug Hillary and Dave Newton have some good articles on the front page of this site on this topic.

Basically, your initial premise is close to correct: UOA's are used to determine proper OCI length through contamination (wear metals, insolubles, fuel....etc) and the rise of TAN, reduction in TBN. As well as a potential indicator of mechanical issues through the possible spikes in various metals (lead, copper....etc), indicate an intake tract leak (silicon increase) and check for coolant or water ingress.

They are not for "tracking wear"; Comparing the performance of different oils to each other, as each lubricant will have its own "signature" in terms of metals and this does not directly correlate with wear.


I've read through all the articles on the front page and while they contain lots of great information, they are certainly not the end-all of discussion and ideas here, and believe I can take this stance because I'm still left with the questions I presented in my original post, even after having read those articles.

More and more frequently on this site, I see people using UOA data to support ideas that seemingly cannot be proven one way or another by UOA data alone. I've presented these questions because, despite all the great info and conversations we've had here, they still remain to be answered.

 

[OVERKILL]

Originally Posted By: RPMster

More and more frequently on this site, I see people using UOA data to support ideas that seemingly cannot be proven one way or another by UOA data alone.


Yeah, I've been involved in many of those arguments, LOL! (hence my post count).

Quote:
I've presented these questions because, despite all the great info and conversations we've had here, they still remain to be answered.


Well, I think we've got the answer. It just seems some are unable to deal with the fact that the $20.00 isn't giving them the definitive and extensive information they think it is

 

[fdcg27]

I think you have a valid point.
What one pays for a UOA has nothing to do with its utility. The lab work involved is highly standardized and inexpensive.
There is more to the information one gets from a UOA than the particle counts.
Sodium and potassium levels are good to know, unless you've used an oil with a sodium add pack and your car uses a potassium free coolant.
Viscosity, TBN and TAN are nice to see, although most of us seem to neglect the importance of oxidation and nitration.
Insoluables seem to be almost universally ignored, although that level is probably of greater meaning than those of the wear metal levels by themselves.
Do wear metals tell us anything?
The particles measured are very small, so an engine could be blowing chunks and you wouldn't see that in a UOA.
Still, I think wear metals per thousand run do have importance.
If they aren't a measure of engine wear, including corrosive damage possibly caused by a given oil formulation, then what are they?
If an engine is really shedding metal at sizes too great to be detected in a UOA, then it isn't likely to live long enough for a second UOA in any event.

 

[INDYMAC]

If you want to learn how to interpret UOA'S, many labs and oil companies offer courses to their customers, and you should take one or two.

I myself haven't taken one, but have used Terry Dyson's services enough to feel comfortable interpretting most of the data. I even feel comfortable using data from different labs if I know what test method theey are using.

I'm afraid most BITOGER's will not be of much help in a professional way with your questions.