Parameters for condition monitoring of engine oil

TBN when depeleted to 25% of new.

Viscosity when thickened or thinned 20% of new

More to it but that is a start.
bruce CLS

Question: Do you care about getting the longest life from your engine or your oil?

Bruce, please give all the parameters which are essential. If i say that new oil is not fit for your engine, how will you prove that it is. Its all for academic interest.
Bob, you should try to answer my query and not divert the attention to something else.Many experts are contributing to this site, i expect them to continue this discussion with open mind.

My question wasn't meant to divert attention but has to be answered before your question can be answered.
Starting with the basics - one problem with answering your question is that diesel engines around the world are quite different in additive content/basetock (Groups 1 -4 with some 5 (ester) added for seal compatibility) and those in US keep changing every couple of years - increasing in soot carrying capability (detergents) while decreasing ZDDP content and increasing antioxidant content - first phenols now more amines. Also TBN becoming of less importance as sulfur in fuels decreases - in US now down to 15 ppm with ULSD fuels required in Jan. '07
So my following terms are basic not meant toward any particular oil
First assuming you don't have water intrusion/coolant leak - need on-line sensor for this since occurence is not time based, the following description is why I said engine or oil life.
When oil first starts out, antioxidants keeping basestock stable - ZDDP reacting with metal surfaces creating antiwear film.
With initial use antioxidants deplete and ZDDP depletes but basestock undergoes minimal changes. Overtime ZDDP depletes so that antiwear film no longer created - wear at start-up initiates but only polishing wear occurs during use since detergent package keeps ZDDP byproducts suspended acting as a solid lubricant - so looking at iron content - iron starts increasing but basestock shows minimal changes since antioxidants still present.
As use further increases, detergents start getting tied up by soot - start losing capability to keep ZDDP by-products suspended - polishing wear accelerates (energy efficiency starts decreasing - lower miles per gallon) - so iron concentration accumulation increases - basestock still minimal changes due to antioxidants
Finally antioxidants deplete, basestock starts oxidizing - however overbased additives neutralize stronger acids and viscosity index improvers keep viscosity stable, polishing wear continues to accelerate as basestock starts becoming acidic - long chain oxidation acids are surface active.
As some point either the acid number or viscosity will increase past specified limit - some use 10% increase others use as high as 50%.
And oil is changed.
This chain of events comes from numerous tests we have run on a past Army program in which used diesel engine oils from field and accelerated seeded fault tests in the lab were used to better understand oil degradation mechanisms of diesel engine oils and to evaluate capabilities of on-line sensors -more important to detect abnormal engines than oil changes.
So if you care about your oil, you run until the additives are totally depleted and change oil when wear amounts (Army uses 400 ppm Fe) or oil parameters exceed set limits (Army has FTIR set of parameters to judge oxidation - becomes tougher as esters added for seal compatibility/additive solubility making C=O band less reliable for oxidation deteremination)
If you care about your engine, you change oil when ZDDP or other antiwear additive depletes, basestock still stable to minimize wear increase and maintain energy effieciency.
Army work and other oil studies presented/in proceedings of NORIA, JOAP (Joint Oil Analysis Program - military), STLE etc. so should be available through their websites.
http://www.noria.com/secure/product_detail.asp?catalogid=92 is one such website
Or you can google Robert Kauffman to find others

Bob,
Thanks for a very elaborate answer,you have described how the additives are functioning, that's Ok.
But I will again request, please chalk out a list of parameters that will decide whether oil in an engine can be continued further or not.You may take example of any engine and any non synthetic oil in it.
We have poured new oil in engine,it is recommended to be changed after 300 hours,just after 50 hours i suspect the oil to be unfit, what parameters will decide that oil is fit to be continued.
We need a clear answer.Which parameters and what are their lower and upper limits? As simple as that.Of course, you may make additive also as one or two parameters in that list.

other than what I listed you can add any wear metal tested in the used oil over 100ppm.

As I said you can add other and have abook full but those 3 are the best IMHO.

More than that I never do unless some odd working condditon such as water is an issue then i would add water to the list or maybe its dirt or dust then that can be added it never ends what to look at depending on the working eviroment maybe you live in a cold area and if the oil fails at a low temp viscosity test than that would be a test also no real answer as I said it depends on enviroment.
bruce

quote:

i suspect the oil to be unfit, what parameters will decide that oil is fit to be continued.

read my post I list 3 things to look at

TBN
Wear metals
viscosoity

If in range of these 3 then it is OK
bruce

Bruce,
you have so simply listed only 3 parameters, i may add some more like
TAN
Dispersancy
Detergency
Extreme pressure Anti wear additive
moisture
Flash point
Insolubles etc etc.

but they are not sufficient in the opinion of experts who themselves are not sure which parameters should be in the list, so many experts are contributing to this site, claiming to know more than all others, i have been trying for the last 3 years, but have not got a single answer. They will answer, but will use many technical words without leading to any conclusion.Their answers are confused while the question is very clear.

Are you sure that only the above parameters are sufficient to decide whether engine oil can be used further or not, will it get approved by oil companies and labs and O.E.M.s ?

I am still inviting the people to answer this simple question : What parameters will decide whether the oil after 100 hours or 1000 hours or 10,000 hours is fit for further use or not.

My take as an observer...

Engine oils are to ideally provide a hydrodynamic film between moving parts as well as to act as a heat transfering medium - thus viscosity limits are important as I have come to understand that viscosity increases appearently decrease thermal transfer rates (likely due to lesser washover/molecule movement/exchange rate at any given location). Cold viscosity would also have some limits as it efects pump-up and flow initiation at the furthers lubrication point from the pump, while pressure relief valves may further hamper such flow/pressure development and is the reason why one reason why it would be wise to not use summer weight oil in the chill of freezing winter. operating viscosity also is important in that while under load, though rotating parts may not be in contact with eachotherin and of themselves, solid matter that happens to find it's way through the oil filter or perhaps become dilodged from a region of the oil passages, could briged the space between the two parts, causing scoring, tracing, or become inbedded. This makes elements such as Si as in dirt ingested through the air intake, etc. a point of concern, as well as related wear metals that are component/location specific depending upon design of the machine (lead and/or aluminum for bearings, etc.). If I recall correctly, high viscosity for both 40 and 100 deg c temps indicates oxidation and/or soot loading, while lower numbers likely indicate fuel loading. Lower 100 deg.c numbers likely indicate shearing of viscosity index improvers (for which I have read such byproduct may impart detergency loading and become part of a sludge matter should such other factors lead to it - such as cold spots, coolant leaks, malfunctioning PCV system...).

I'll continue later, but ask yourself this -"What is it that a lubricant is suppose to due?" With that, you just might fine things starting to come together, while also remembering that the heat and shearing, along with all the other environmental factors that impact the fluid and the way it operates, work against a balanced formulation of base oil and additives, and for which the additives are sacrificial and ultimately in place to support the base oil and impart benefits to it's purpose of use.

Take care.

quote:

What parameters will decide whether the oil after 100 hours or 1000 hours or 10,000 hours is fit for further use or not.

I told you the top 3 tests That i use no others are needed to give answer you need BUT YES you could come up with perhaps 100 tests to run but the praticle answer is covered by my 3 tests to run more tests the cost and any time spent is not repayabel in better data or long oil use interval. Or put it this way take a oil come up with 100 tests or data points to look at, any kind you can think of and 97 of them are not needed to decide if oil needs to be chnaged out or not.

bruce

no disrespect to you but you question is just like asking "how high is up" there is no correct answer.
bruce

I guess one could add "insoluables" to the list, with some eye on coolant indicators such as potasium and sodium IIRC. Silicon levels alone could indicate sealants, where as elevated silicon along with increase wear metals would lead me to think dirt ingestion. As for other levels, whether new or used-up, they will still show-up elementally, which brings one back around to such change indicators as that shown as consequences of the lube oil's decline it's ability to protect as noted by others - TBN and/or nitration for acid neutralization capacity, wear metals as result of dirt/coolant dilution/fuel dilution/condensate/shear thinning/overall add-pack depletion, and viscosity.

I'm no expert mind you, but have you looked over some UOA's and observed the lab's recommendations in different cases?

Take care.

Dear Mr.Prabhakar Agarwal,
All the parameters mentioned in the above posts are good enough to assess the serviceability of the engine oils.But for different engine manufactures,the engine metalurgy and engine design will be different and so as the warning limits.

if the physico chemical parameters and wear metals are well within that limits,I do not see any risk to take the same engine oil to further.