Understanding TBN in Modern Heavy Duty Engine Oils

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http://www.ccjdigital.com/partner-soluti...ty-engine-oils/ Understanding TBN in Modern Heavy Duty Engine Oils Content Below is Presented By: Sponsored Information Published on May 31, 2017 Historically, Total Base Number (TBN) has been perceived as a key indicator of remaining useful oil life in heavy-duty engine oils. While acid neutralization is still an important function of engine oil, changes in engine design and the move to Ultra Low Sulfur Diesel (ULSD) fuels have decreased the amount of acids produced in the engine and influenced oil formulations over the last decade. This article explains the differences in ASTM test methods for TBN, industry changes leading to the current categories, and the change in how TBN values may be interpreted with the new oils. The Test Methods ASTM D2896 is the test method most commonly used to measure TBN on new oils. Use of a very strong acid identifies both “hard” and “soft” TBN, giving the total alkalinity reserve of the sample. The value obtained from this test is the number reported on most technical data sheets. ASTM D4739 is the test favored by oil analysis labs on used oil samples. Using a weaker acid, it only identifies alkalinity from metallic elements like calcium, magnesium, and zinc. These metals are often doing double-duty in the oil (calcium provides detergency and also acid neutralization; zinc in the popular anti-wear additive ZDDP also contributes to anti-oxidation). This test does not identify newer ashless (i.e. non-metallic) additives, and reported values will be lower versus ASTM D2896. API CJ-4 to CK-4 When the industry updated from API CI-4 / CI-4+ to API CJ-4 oils, the new oil chemistry differed from those of previous service categories. To safeguard the effectiveness and service life of exhaust after-treatment devices, API CJ-4 limited sulfated ash to no more than 1%, and oils were formulated with lower levels of metallic additives and new ashless additives. This resulted in finished oils with lower TBN under the ASTM D4739 method versus the previous category. As a result of increased levels of ashless anti-oxidants, many current CK-4 oils may reflect a higher initial TBN via ASTM D2896 than previous CJ-4 versions, but those same new oils will also likely reflect an even lower TBN via ASTM D4739, due to the decrease in over-based metallic detergents (which create ash when burned, leading to engine deposits). The table below illustrates the differences one might see in initial observed TBN values, depending on the API specification claimed and testing method used: Volvo / Mack T-13 – New Industry Test for Oxidation Stability If TBN is no longer the best measure of useful oil life with regard to oxidation stability, how do we know that the new oils are up to the task? Mack addressed this topic with the inclusion of their test protocol as part of the new API CK-4 standard as well as Volvo / Mack’s own proprietary VDS-4.5 specification. This new test evaluates the candidate oil’s oxidation stability, nitration and resistance to bearing corrosion. CJ-4 technology generally cannot pass this test without a significant antioxidant boost, making the T-13 test a critical part of the new CK-4 standard, as well as setting the performance limits for Volvo / Mack’s VDS-4.5 specification. Passing this grueling test indicates a significant increase in oxidation protection even at lower TBN values by ASTM D4739. Putting It All in Perspective As additive chemistry has shifted, the standard TBN testing protocol simply doesn’t provide the same level of insight that it once did. When looking at used oil analysis reports, the full range of available data should be considered. If TBN appears to be low but all other criteria are good (low wear metals, corrosion control, viscosity / oxidation control), there is likely little reason to worry.
 
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Originally Posted By: FermeLaPorte
Just change oils every 3 months. It can't fail you.
This line of reasoning isn't really supported by evidence or facts.
 

dnewton3

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Originally Posted By: wemay
http://www.ccjdigital.com/partner-soluti...ty-engine-oils/ ... When looking at used oil analysis reports, the full range of available data should be considered. If TBN appears to be low but all other criteria are good (low wear metals, corrosion control, viscosity / oxidation control), there is likely little reason to worry.
I have so been saying this for several years. TBN (and TAN crossover) don't mean nearly as much as they did two decades ago. Finally it's in print elsewhere and just maybe some of you might pay attention.
 
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Originally Posted By: wemay
http://www.ccjdigital.com/partner-soluti...ty-engine-oils/ Putting It All in Perspective As additive chemistry has shifted, the standard TBN testing protocol simply doesn’t provide the same level of insight that it once did. When looking at used oil analysis reports, the full range of available data should be considered. If TBN appears to be low but all other criteria are good (low wear metals, corrosion control, viscosity / oxidation control), there is likely little reason to worry.
So does this mean that we need to start asking for oxidation and nitration readings on UOA's instead of TBN?
 
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Good read, but in all honesty has anyone ever seen a low TBN on any diesel UOA? I sure have not and so I do not place much importance on that particular attribute--gasoline engines are a different matter.
 
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Originally Posted By: 2015_PSD
Good read, but in all honesty has anyone ever seen a low TBN on any diesel UOA? I sure have not and so I do not place much importance on that particular attribute--gasoline engines are a different matter.
Since you're asking, yes, I have seen numerous diesel UOA's with low TBN's.
 
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Originally Posted By: bigj_16
Since you're asking, yes, I have seen numerous diesel UOA's with low TBN's.
I have only been checking since 2015, but I daresay that low TBN in a diesel UOA is an exception and not the rule. You may have seen some, I will search again and see what I find.
 

dnewton3

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It's not a question of a low TBN. (I do think it's not all that common; at least in my data). The on-the-surface question is do you see low TBN and high wear? Ummmmmmm .... No. But, the underlying question is this: Is there correlation between wear rates and TBN retention? Absolutely NOT!
 
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Originally Posted By: dnewton3
It's not a question of a low TBN. (I do think it's not all that common; at least in my data). The on-the-surface question is do you see low TBN and high wear? Ummmmmmm .... No. But, the underlying question is this: Is there correlation between wear rates and TBN retention? Absolutely NOT!
Agreed; simply because unlike the potential in a gasoline engine, I do not see a correlation between TBN and "anything" in a diesel. The combustion process and the by-products are different. From what I observe, acid creation does not happen as it does in a gasoline thus TBN has marginal, if any, impact on wear rates in a diesel.
 
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Once USLD hit the market starting TBN was able to be reduced, prior to USLD it wasn't uncommon to see HDEO with a starting TBN of 12 and premium oils were in the 15 neighborhood.
 
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Originally Posted By: 2015_PSD
simply because unlike the potential in a gasoline engine, I do not see a correlation between TBN and "anything" in a diesel. The combustion process and the by-products are different. From what I observe, acid creation does not happen as it does in a gasoline thus TBN has marginal, if any, impact on wear rates in a diesel.
What do you think is in the exhaust that gets re-breathed with EGR in a diesel? NOx, specifically NO2, from oxidation of nitrogen in the higher-than-gasoline combustion temps of a diesel. NO2 then gets converted to HNO3, nitric acid, in the presence of water vapor, another obvious combustion product. Nitric acid is a strong acid (like sulfuric) and reacts with alkaline detergents, or else causes corrosion. Modern diesels DO need alkaline buffering in the oil especially since they all come with EGR. They just need less since the sulfur is gone (in many countries, not all)
 
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Originally Posted By: m37charlie
Originally Posted By: 2015_PSD
simply because unlike the potential in a gasoline engine, I do not see a correlation between TBN and "anything" in a diesel. The combustion process and the by-products are different. From what I observe, acid creation does not happen as it does in a gasoline thus TBN has marginal, if any, impact on wear rates in a diesel.
What do you think is in the exhaust that gets re-breathed with EGR in a diesel? NOx, specifically NO2, from oxidation of nitrogen in the higher-than-gasoline combustion temps of a diesel. NO2 then gets converted to HNO3, nitric acid, in the presence of water vapor, another obvious combustion product. Nitric acid is a strong acid (like sulfuric) and reacts with alkaline detergents, or else causes corrosion. Modern diesels DO need alkaline buffering in the oil especially since they all come with EGR. They just need less since the sulfur is gone (in many countries, not all)
Show me a UOA with a high TAN that warrants worrying about it. I have never seen a single one; have you?
 

dnewton3

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I'd agree that all internal combustion engines running on fossil fuels are going to need some amount of acid fighting components; typically the TBN to combat TAN is how we refer to it. However, after seeing a lot of UOAs where TAN crosses over TBN, and yet nothing happens to wear rates, I'd say it's essentially moot. Are bases needed? Yes. To what extent? Hard to say because most OCIs don't run long enough to see the effects of TAN play out. Back in the old days there were things that contributed to greater concerns; higher sulfur in the fuels and also open PCV systems allowed more moisture in. Those concerns are not present in engines from the last decade. Admittedly more use of EGR does induce stuff to watch, but apparently it's not nearly as horrible as we'd first believe or we'd see all manner of chaos in UOAs. And we don't. This is the manifestation of the concepts I try to get folks to look at. Inputs are only predictors of potential changes. (Vis, FP, insolubles, TBN/TAN, etc ...) Output tell you what actually happens. (wear metals, PCs and such)
 
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