TBN vs. Wear Numbers

[skyship]

Originally Posted By: bigjl
One interesting thing I have noted is that a lot of the mid to low saps oil seem to have TBN less than 10 sometimes less than 8 when "virgin".
But these same oils are also used over long OCI, for example my Pathfinder has an 18,000mile OCI, though I am changing much less than that too be honest as I am of the opinion that oil and a filter is less than a camchain, turbo or crankshaft.
And there is a strange satisfaction knowing that if just short of you normal OCI you could undergo a 1000mile emergency journey with no issues.
I am sure there is a reason for the low TBN's I have mentioned above.


Some very good full synthetic long life oils have a TBN less than 10, but I can't think of one less than 8.
Nissan make good diesels, but 18K miles is interesting as that is on a par with VW and Audi, so I hope they are listing a severe service OCI of 10K miles or something more realistic for inner city or off road types.
Some of the latest additives don't show up so well in the cheaper UOA, but I thought it was just the anti wear ones that don't, so I wonder if they have something else for detergent not based on Calcium.
Detergents are more important to a diesel engine than they are to a gas guzzler, so I would think more than twice about using a low TBN oil for a long service interval.

 

[chubbs1]

I say try the experiment you lined out in your original post.

 

[skyship]

Originally Posted By: Artem
The OPs example doesn't relate to real life UOA results.
UOA from my 07 Civic EX showed the same wear numbers after 6,800 miles and 12,000 mile UOAs, so the 2x the wear after putting on 2x the mileage thinking is severely flawed.
It's still hard to say because with the oil filter getting more efficient with use, the wear could really be increasing some but since the oil filter is catching all the particles, it's not showing up in the UOA report....


The worst wear rates are for the first few thousand miles after new oil & filter, then there is a kind of flat section where wear rates are constant and finaly they soar up as the additives fail, the filter blocks, the oil shears or just gets so much carbon it goes out of any sensible viscosity range.
Hard to figure out without doing particle counts etc if an increase in wear rate is caused by the oil breaking down but offset by the increasing efficiency of a dirty filter, to the point at which the oil should have been changed.
I'm a fan of the cleanish oil and dirty filters club, so I only change oil filters at the manufacturers normal or max figure, BUT always ditch the oil at 10K km. It's [censored] trying to explain that to a German garage dipstick as they think you have gone nuts and I bet the problem is worse in the US. The paperwork has to be correct in Germany and they just don't know what to write.
A lot of marine diesels and the small hybrid cars do 2 for one OCI's and they are catching on with the use of new Long life oil filters, BUT never drain and refit an oil filter only fuel filters, because you can start an oil leak.

 

[Phishin]

Originally Posted By: gfh77665
If you cannot understand the difference between "rate" and "amount", then I am sure you cannot understand it at all.


Actually man, you make no sense here. So, instead of bashing people, take a look at what you wrote....

Because I'm saying the "rate" never changed. Therefore, neither did the amount, really. In my example, let's say I'd have 10ppm of Iron at 5k miles with a TBN of 1.0 But in my same example, I'm saying I'd have 20 ppm of Iron at 10k miles with a TBN of 0.0. Then if I took it out to 20k miles, I'd have 40ppm of iron in my oil and the TBN would still be 0.0

So, to make it clearer to you bro, if I changed my oil at 5k miles for 4 OC's (assuming a 4 quart sump), I'd be removing 16 quarts of oil that each have 10ppm of iron in there. That comes out to a total mass of iron of 0.15 grams.

If I never changed my oil again for the next 20k miles, I'd have 4 quarts of oil at 40ppm of iron.....which is also 0.15 grams of iron.

I had the same wear regardless how often I changed my oil.

 

[skyship]

Originally Posted By: Phishin
Originally Posted By: gfh77665
If you cannot understand the difference between "rate" and "amount", then I am sure you cannot understand it at all.


Actually man, you make no sense here. So, instead of bashing people, take a look at what you wrote....

Because I'm saying the "rate" never changed. Therefore, neither did the amount, really. In my example, let's say I'd have 10ppm of Iron at 5k miles with a TBN of 1.0 But in my same example, I'm saying I'd have 20 ppm of Iron at 10k miles with a TBN of 0.0. Then if I took it out to 20k miles, I'd have 40ppm of iron in my oil and the TBN would still be 0.0
So, to make it clearer to you bro, if I changed my oil at 5k miles for 4 OC's (assuming a 4 quart sump), I'd be removing 16 quarts of oil that each have 10ppm of iron in there. That comes out to a total mass of iron of 0.15 grams.
If I never changed my oil again for the next 20k miles, I'd have 4 quarts of oil at 40ppm of iron.....which is also 0.15 grams of iron.
I had the same wear regardless how often I changed my oil.


Got me real confused too, can we see a graph?
My tyre and socks wear rates are fairly constant!

 

[Artem]

Originally Posted By: Phishin
Originally Posted By: gfh77665
If you cannot understand the difference between "rate" and "amount", then I am sure you cannot understand it at all.


Actually man, you make no sense here. So, instead of bashing people, take a look at what you wrote....

Because I'm saying the "rate" never changed. Therefore, neither did the amount, really. In my example, let's say I'd have 10ppm of Iron at 5k miles with a TBN of 1.0 But in my same example, I'm saying I'd have 20 ppm of Iron at 10k miles with a TBN of 0.0. Then if I took it out to 20k miles, I'd have 40ppm of iron in my oil and the TBN would still be 0.0

So, to make it clearer to you bro, if I changed my oil at 5k miles for 4 OC's (assuming a 4 quart sump), I'd be removing 16 quarts of oil that each have 10ppm of iron in there. That comes out to a total mass of iron of 0.15 grams.

If I never changed my oil again for the next 20k miles, I'd have 4 quarts of oil at 40ppm of iron.....which is also 0.15 grams of iron.

I had the same wear regardless how often I changed my oil.


Iron goes up with mileage, so your calculations regarding iron and mileage could be realistic. It's the other metals that matter though, as they show increased wear, if they skyrocket x4.

 

[dnewton3]

If my TBN were decent and the TAN were below it, and wear was good, I'd keep driving it.

If the TBN/TAN relationship inverted, I'd be in cautionary observation mode.

UOAs seldom have a singular reason to condemn a fluid; one tracked criteria is not a reason to panic. Only if the issues were grossly over a limit would I pull the plug (literally). And typically when something like that happens, it's accompanied by other tell-tale signs in the engine bay (loss of coolant, dirt ingestion with dust in the intake tract, etc). Wear metals themselves have condemnation limits so high that most of us BITOGers will NEVER see them. Other issues (soot, insobubles, TBN/TAN, etc) in concert with each other will condemn a fluid.

I'm a big fan of pushing lubes out, but safely. As we get closer to the edge of the TBN/TAN envelope, then other monitoring techniques should be used along with the UOA. If nothing else, pop off a valve cover and make visual observations of sludge (or hopefully the lack of it).

I recall seeing my first OEM 7.5k mile OCI recommendation in an owner's manual; it was my 2000 Nissan Frontier 3.3L v-6. I thought how garishly long that was. Now, I think there is merit to it, and probably that (in a well running, mechanically sound engine) that 7.5k miles is actually conservative, if other items are all in check.

As my sig line says; any product can be over or under utilized.

 

[Garak]

Originally Posted By: skyship
Some very good full synthetic long life oils have a TBN less than 10, but I can't think of one less than 8.


True, but you do have to keep in mind that there are some examples, at least in North America, that lack the ACEA ratings, and therefore don't have to have a minimum TBN of 8 (I think that's what the minimum is for some of the ACEA specs). For example, you can compare even some SN/GF-5 North American synthetics (M1, PP) that meet something like A1/B1, versus PC Supreme Synthetic which has a TBN of around 7.9, missing the limit and having no corresponding ACEA specification.