Understanding TBN in Modern Heavy Duty Engine Oils

[CarbonSteel]

Originally Posted By: dnewton3

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.

I agree with needing some TBN, but I have never seen a diesel UOA that TAN has crossed TBN, much less where it would be an issue contributing to wear so I do not place a high value on having a large starting TBN in a diesel oil. Dave - you have a large stack of UOAs, have you seen any?

 

[m37charlie]

In my 09 BMW the EGR malfunctioned and as a result TAN went up to 8.07 TBN was down around 1.5 and iron was 152. Res ipsa loquitor. This was on weak LL04 oil. It would be interesting to reproduce this situation on Delvac 1 SHC but unfortunately it is not reproducible.

 

[dnewton3]

Yes - I have UOAs where crossover happened. It's not common in diesels now days. When it does happen, it typically is not correlated to any wear issues. However, as Charlie shows, it can be a big deal. But not because of "normal" operation. Rather, only a mechanical failure indirectly induced the wear escalation. Charlie - did the BMW start running badly, and you noticed the EGR affected performance? Or, did the engine "throw a code" (MIL)? I doubt the UOA brought it to your attention initially. Let's not forget that the most common additives used for "bases" (Ca, Mg, et) are also helpful in other manners such as cleaning and lubricating. So there will almost always be a need to have a decent amount of base additives. But the need for super-high TBN (12+) just isn't there today like it was in yesteryear.

 

[CarbonSteel]

Originally Posted By: dnewton3

Yes - I have UOAs where crossover happened. It's not common in diesels now days. When it does happen, it typically is not correlated to any wear issues. However, as Charlie shows, it can be a big deal. But not because of "normal" operation. Rather, only a mechanical failure indirectly induced the wear escalation.

Thanks Dave and for clarity I was only referring to normal operation. There will always be the special case that causes problems, but those are the exception and not the rule.

 

[m37charlie]

In about 2.5 yrs I am going to start the ultimate UOA as far as sulfur and TBN/TAN. Anchorage to Halifax (5200mi each way), then Halifax to Antwerp by roro, then to Montevideo...then ~30Kmi around S.America on fuel 50-800ppm sulfur. Fortunately my engine uses 0.4ml/mile so over 40K mile it will take 16L in makeup out of 29.6L capacity. But we will see if 30Kmi of medium sulfur fuel makes a significant drop in TBN.http://bevo.mercedes-benz.com/bevolisten/136.2_en.html posted sulfur contents need to be taken with a grain of sulfur, usually higher than advertised in many places. I am not planning on changing the oil, just adding makeup.

 

[m37charlie]

Originally Posted By: dnewton3

Yes - However, as Charlie shows, it can be a big deal. But not because of "normal" operation. Rather, only a mechanical failure indirectly induced the wear escalation. Charlie - did the BMW start running badly, and you noticed the EGR affected performance? Or, did the engine "throw a code" (MIL)? I doubt the UOA brought it to your attention initially. Let's not forget that the most common additives used for "bases" (Ca, Mg, et) are also helpful in other manners such as cleaning and lubricating. So there will almost always be a need to have a decent amount of base additives. But the need for super-high TBN (12+) just isn't there today like it was in yesteryear.

No code that I know of, my daughter said "exhaust smelled bad". No steam in exhaust, no water, glycol or K/Na in oil. I went 13K mile on that OCI and dealer replaced EGR cooler and valve under warranty. Later, EGR, DPF and Nox reduction catalyst ended up under tarp in front yard. Charlie

 

[dnewton3]

Originally Posted By: m37charlie

In about 2.5 yrs I am going to start the ultimate UOA as far as sulfur and TBN/TAN. Anchorage to Halifax (5200mi each way), then Halifax to Antwerp by roro, then to Montevideo...then ~30Kmi around S.America on fuel 50-800ppm sulfur. Fortunately my engine uses 0.4ml/mile so over 40K mile it will take 16L in makeup out of 29.6L capacity. But we will see if 30Kmi of medium sulfur fuel makes a significant drop in TBN.http://bevo.mercedes-benz.com/bevolisten/136.2_en.html posted sulfur contents need to be taken with a grain of sulfur, usually higher than advertised in many places. I am not planning on changing the oil, just adding makeup.

I always look forward to your info from you because you're somewhat of a "fringe" operation. Most folks don't run the equipment that you do, in the environment that you do. Always interesting to see how well you fare. Certainly will be interesting to see how the S plays out on TBN and such. Although a ways out, I wish you good luck on that trip, Charlie! And I trust you'll post interesting stuff along the way for us to follow!

 

[dustyroads]

Originally Posted By: 2015_PSD

Originally Posted By: dnewton3

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.

I agree with needing some TBN, but I have never seen a diesel UOA that TAN has crossed TBN, much less where it would be an issue contributing to wear so I do not place a high value on having a large starting TBN in a diesel oil. Dave - you have a large stack of UOAs, have you seen any?

I've done dozens of UOAs for my heavy duty diesels over the years and in all of them where I had the TAN tested, it had overtaken the TBN. I'm sure that I have posted a few of them here in my short time at BITOG. I think there was one with TBN of 0.7 and TAN was 4.4 (?) and maybe others of similar numbers. The paragraph above is just FYI, nothing more, as the wear rates were very low with no signs of bearing corrosion. For the last couple of years, I've been using ALS labs and only getting TBN, or with the Delvac Accutrack kits going to ALS's Kansas City lab, neither TBN nor TAN is given. I don't get concerned about TBN/TAN although Detroit Diesel says that the oil should be changed when TBN is down to one-third of starting TBN (no mention of TAN). CK-4 oil seems to be much better at TBN retention, anyway.

 

[zeng]

Quote:

I've done dozens of UOAs for my heavy duty diesels over the years and in all of them where I had the TAN tested, it had overtaken the TBN. I'm sure that I have posted a few of them here in my short time at BITOG. I think there was one with TBN of 0.7 and TAN was 4.4 (?) and maybe others of similar numbers. The paragraph above is just FYI, nothing more, as the wear rates were very low with no signs of bearing corrosion.

Mind sharing miles in use ? I presume they are HDEO CJ4 oils.

 

[dustyroads]

Originally Posted By: zeng

Quote:

I've done dozens of UOAs for my heavy duty diesels over the years and in all of them where I had the TAN tested, it had overtaken the TBN. I'm sure that I have posted a few of them here in my short time at BITOG. I think there was one with TBN of 0.7 and TAN was 4.4 (?) and maybe others of similar numbers. The paragraph above is just FYI, nothing more, as the wear rates were very low with no signs of bearing corrosion.

Mind sharing miles in use ? I presume they are HDEO CJ4 oils.

Sure, I went back and found 3 reports that I posted here. Before I found BITOG I was using mostly Cat SOS and some Delvac Accutrack and asked for paper copies to be sent home. Those UOAs are long gone, and I didn't always get TBN/TAN, but some were CJ-4 and earlier samples (prior to 2006) would have been previous API categories. The reports below are from Blackstone.

Code:

All of these are from my 2012 Volvo with a Volvo D11 (10.8L) engine used in OTR use and mostly loaded to near 80k lbs.

June 2013
19,694 miles/679 hours
Delo 400LE CJ-4 15W-40

Aluminum 5
Chromium 0
Iron 9
Copper 5
Lead 3
Tin 5

TBN 0.7
TAN 4.4
-----------------------------------

Late 2013
23,294 miles/575 hours

Delo XLE 10W30

Aluminum 4
Chromium 0
Iron 8
Copper 3
Lead 2
Tin 3

TBN 1.8      Virgin VOA TBN 9.1
TAN 4.6                 TAN 3.4
---------------------------------------

Late 2014 
24,346 miles/694 hours
Shell Rotella T 15W-40

Aluminum 4
Chromium 0
Iron 11
Copper 2
Lead 1
Tin 0

TBN 3.3
TAN 5.2

Edit- all of these show TAN has overtaken TBN, but still very low wear rates and no signs of the bearings being attacked by acids.

 

[zeng]

Huuh .... your HDEO UOA at 20-24k miles have far more impressive metal wear rates than most PCMO UOA's at OCI of 5-10k miles.

 

[CarbonSteel]

Originally Posted By: dustyroads

Edit- all of these show TAN has overtaken TBN, but still very low wear rates and no signs of the bearings being attacked by acids.

Dusty - thanks for sharing. According to what I have been told by two UOA labs, until TAN rises above 8.0 it is not acidic enough to cause accelerated wear which **may** explain why even though TAN crossed TBN there was still no abnormal wear. My fuel dilution will force me to change my oil long before TAN is even a consideration which is why TBN takes a back seat to other attributes in the UOA (only speaking of my situation).

 

[dnewton3]

I agree - I don't think I have a single UOA from a "normal" application (defined as no mechanical issues in the equipment) where TAN ever went above 8; typically lower than that most often. Crossover happens in many UOAs that go past 5-7k miles. But there's no shift in wear. TBN is important for ultra long OCIs. Short of that it's moot. And one can always to "top off" to help bolster a waning number; just as Charlie plans.