Relevance of TBN

[haley10]

Since this is the gasser forum, I'm wondering if we don't make too much of TBN? If an oil is formulated to resist oxidation and shows a lower TBN than an oil that will oxidize more rapidly but has a high TBN, is that not better??

TBN is obviously important with diesels, but I wonder if we don't make too much of it here?

If an oil is very much resisting oxidation, then it doesn't have to clean up after itself as much. I think I'm starting to see why some labs give TAN for gassers on uoa's.

I'm not going to evaluate any pcmo's based on better TBN #'s anymore. The anti-oxidants and base may be much more relevant.

I'm thinking we mislead ourselves sometime by thinking one oil is better and another is weak based on TBN, but we often don't know how one is resisting oxidation better than the other and therefore not depleting the add pak.

Just wanted to inspire some discussion.

 

[haley10]

From what I can figure out, some OLM's try to calculate based on depletion of typical AW agents, such as ZDDP. UOA doesn't show you this.

So a good TBN maybe doesn't tell you the oil is good if you don't know the total acidity or the state of the additive pak otherwise.

 

[TooSlick]

Spectrographic analysis, including FTIR to evaluate oxidation/nitration, does tell you how depleted the AW additives and FM's are...

The key is you have to evaluate the UOA in a holistic manner, and understand the dependencies of the various bits of data.

 

[haley10]

quote:

---

Originally posted by TooSlick:
Spectrographic analysis, including FTIR to evaluate oxidation/nitration, does tell you how depleted the AW additives and FM's are...

The key is you have to evaluate the UOA in a holistic manner, and understand the dependencies of the various bits of data.

---

Well, that's why I get people like you and Terry to evaluate rather than try to do it myself. But, my lab doesn't give any oxidation/nitration figures or TAN, just insolubles and TBN if requested.

Don't you think we make more of TBN on uoa's measured at one point in time than it's really worth for pcmo's? It seems like the board thinks and some of the canned labs computer programs think if the TBN is above a certain level then your good to go. That's basically what I'm challenging here.

We see to get a lot of ballyhoo here about Hdeo's because of the TBN, but it might not be relevant on that point alone. I'm not referencing any of your recommendations at all, just the Delo must be better than Chevron because of the TBN argument.

[ August 02, 2005, 02:05 PM: Message edited by: haley10 ]

 

[TooSlick]

ZDDP is also the primary anti-oxidant used in lubricants of all types. So if oxidation and/or total solids are high, the AW additives are correspondingly depleted. For example, if the Boron level drops to 25% of its' baseline value, I'd change the lube simply based on that alone.

You have to look at the whole picture with UOA's to determine if the lubricant is still servicable - and how much margin you have. There is not an easy way to explain it. Gas engines will normally show too much oxidative/evaporative thickening before the TBN bottoms out. In many other cases, contamination from dirt,coolant and fuel is the condemning factor and not reserve detergency.

In other words, TBN is the "dependant variable" and is a reflection of many types of contamination - organic acids,raw fuel, solid carbonacous materials, internal/external leaks, etc...

The final thing to keep in mind is the concept of additive balance. For example, HDEO's require about 50% more ZDDP to balance out the high levels of alkaline detergent additives (10-12 TBN), necessary to combat soot and fuel related, sulphuric acid. A properly balanced PCMO will have correspondingly lower levels of each and still provide excellent protection

 

[Pablo]

Well posted and I tend to agree - I only wish oxidation measurement was more standardized and comparable - even with the same lab, same car, same oil it's a difficult relative number to use.

 

[haley10]

Thanks TS, very informative. I ask and therfore I learn. With ZDDP being reduced and Amsoil formulating thinner, I may have more questions in the future. I think I need 12 cst of GC or ATM, but..............

 

[Bryanccfshr]

Great info Tooslick
I also may have questions concering reduced ZDDP and the use of boron , calcium and moly to carry some of that load.

 

[fuel tanker man]

If there's one thing I've learned here, it's that TBN's matter--unless it's Redline, and then they don't matter.

Redline can get away with fractional TBN's because, well... because.

Dan

 

[haley10]

Castrol fomulations don't show boron so it's difficulr to look at as a factor. Obviously no MoDTC as anti-oxidant either.

 

[Bryanccfshr]

This is similar to a another post in interesting articles.
I agree that a high TBN may not be neccesary in a modern fuel injected ECM tuned engine. TBN is simply a number. It doesn't really tell us how well that additive package can work in a vehicle, it must be formulated to deal with specific contaminants. Diesel soot is differnt than blowby from a gas engine and the temperatures the oils are exposed to can differ.
I am concerned that oils can be designed to have and maintain a high TBN but by maintaining a high TBN does that make it a beter oil? Or simply an oil with a lazy additive package that is so slow to react with contaminats the TAN can overwhelm the rate the high but slow to work TBN can clean up?

Good topic.

 

[MolaKule]

quote:

---

For example, HDEO's require about 50% more ZDDP to balance out the high levels of alkaline detergent additives (10-12 TBN), necessary to combat soot and fuel related, sulphuric acid. A properly balanced PCMO will have correspondingly lower levels of each and still provide excellent protection

---

HDD's or HDEO's require more AW additive such as ZDDP in order to reduce valve train wear in highly loaded diesel engines.

The dispersants suspend the soot. The detergents, both organic and organo-metallic detergents, keep the tbn from falling due to sulfuric and nitric acids as a result of fuel combustion.

ZDDP is only ONE of the anti-oxidants used in fully formulated PCMO's and Heavy Duty Diesel (HDD's as they are now called) oils.

HDD's have an uphill battle in terms of oil thickening for two reasons:
1. Oxidation
2. Soot

Both oxidation and soot retention increase the viscosity of HDD's. Both soot and oxidation by-products want to polymerise and thicken HDD's.

Special dispersants soften the soot and hold it in suspension until drain time.

 

[thedawk]

I like your question and reasoning haley10. I also recall learning from posts here that a high TBN is not necessary in deciding on an oil, just watch the percentage it depletes in a given OCI comparede to another oils percentage in a given OCI. For example, oil (A) started with a TBN of 10 and after 5000 miles had a TBN of 2. Oil (B) started with a TBN of 8 and after 5000 miles had a TBN of 3. Oil (B) held up better and would last longer than oil (A). That's the way I understood the info from TBNs and UOAs. Am I way off base here?

 

[Whimsey]

From what I've seen with the Schaeffer Supreme 5W-30 TBN depletion is not linear with the miles accumulated. It starts at 7, non Blackstone measurement, and at 4,000 miles it's 2 and at 8,000 miles it's 1 with Blackstone measurement, which is less than the "usual" measurement number. So in 4,000 miles "extra" miles it loses only "1 TBN" over the initial 4,000 mile OCI.

Whimsey

 

[Doug Hillary]

Hi,
Molakule - you said;
"HDD's have an uphill battle in terms of oil thickening for two reasons:
1. Oxidation
2. Soot"

That has been my practical experience and one reason why I changed from a mineral to semi-synthetic then finally to a fully synthetic HDD

A fully synthetic HDD is likely to better resist oxidation and with an advanced additive package, more able to handle soot in a non abrasive way. Again my experience over the last several decades has shown this to be so

A centrifuge separator GREATLY assists in managing soot during seriously extended OCIs

As stated elsewhere I have never had to change oil due to either;
a) a depleted TBN
b) a high TAN
c) viscosity out of agreed OEM/Oil Co parameters

The main OC reason has always been that one of the time, distance, soot or iron limits having been reached

In the case of viscosity it has actually never varied from more than -3% to +6% of the virgin product even at 125kkms OCI. Confirmed of course by hundreds of UOAs on my database

In using both HDD and PCMO synthetics in a variety of petrol engines;
the highest TAN I have recorded is 4.6 (for both)
the lowest TBN has been 7 (for both with starting TBN of 12-12.7)

This is for an OCI out to 20kkms and /or twelve months whichever is reached first

Regards

Doug

[ August 03, 2005, 09:25 PM: Message edited by: Doug Hillary ]

 

[Terry]

Molakule and Doug, accurate posts, thanks for clarifying the thread a bit.

TBN is a relative reading or the reserve acid fighting capability of a lube and needed in my work for extended drains regardless of fuel type.
It can be inaccurate or misleading in that TBN of a chemistry may test "high" but actually be ineffective in resisting acid formation.

Acid formation in the US modern diesel or gas engine properly maintained ,is low compared to say 20 years ago.

Now in Dougs neck of the woods environment and fuel quality change that lots.

This is were the chemistry cause and effect must be properly understood and in a "holistic way as Ted states. Holistically acurrate or you chase rabbits into holes that lead no where.

Ted I have seen wear control perfect with soot/solids/ sludge forming out of moving parts way but preparing to come loose or clog vented areas, thus FTIR readings skew upward while wear is low.

 

[TooSlick]

TD,

Indeed, this is why I like to see oxidation and nitration broken out individually in Abs/Cm, rather than just lump everything as total solids. Particularly in a diesel engine, total solids so closely mimics the soot level that it's very hard to isolate the other parameters.

I'd agree that if you consistently see abnormal oxidation/nitration with normal service intervals, it's an indirect sign that gunk is forming.

But hey, you've got another big Yacht payment coming up - so enough free info for this day...