TBN depletion good or bad?

[Ausfahrt]

Please consider the following hypothetical situation:

Two identical cars are driven 10000 miles in identical conditions with synthetic oil. The cars had different brands of oil but both oils started with a TBN of 12.

The old oil from car #1 had a TBN of 2.3 after the test run and the old oil from car #2 had a TBN of 5.7 after the same test run.

So, ALL OTHER THINGS BEING EQUAL, is an oil that depletes its TBN during its time in an engine like car #1 doing a better or worse job of protecting that engine from wear than an oil that retains more TBN like car #2?

 

[Steve S]

Get a TAN [total acid number] to see which is better .

 

[hate2work]

Originally Posted By: Steve S
Get a TAN [total acid number] to see which is better .


He said all other things being equal.

Both oils protected the engine the same, IMO.

 

[dgee]

 

[Quattro Pete]

Originally Posted By: bigdreama
So, ALL OTHER THINGS BEING EQUAL, is an oil that depletes its TBN during its time in an engine like car #1 doing a better or worse job of protecting that engine from wear than an oil that retains more TBN like car #2?

I'd say it's impossible to infer from this.

 

[joel95ex]

Most likely they are protecting the same, but the lower number will protect for a shorter time/has less "useful" life left.

 

[JHZR2]

So one oil has a different TBN depletion rate than the other, big deal.

The buffering capacity is still there.

However, one thing that needs to be proven: remember doing titrations in HS chemistry. You have an indicator in a solution, and then you titrate something in until you see a color change? Well, remember what happens when you get close? You start to see spurts of color, which then change back. As you get closer and closer to equivalence, the color takes longer and longer to go away.

I look at low TBN the same way. Having lots of active additive is better than less. In some ways it becomes a random interaction/probability scenario type thing... the more buffer molecules you have, the better chance that one is going to hit, and the more hits you have, the higher chance of a reaction.

So in my view, while buffering capacity is still maintained in both, there may be a differential term that has a varying buffering rate, which must be considered.

 

[rclint]

JHZR2

Is that the way TBN is checked, they use a known marker of TBN, then check for that single marker (be it titration or whatever.. also do you know if they use titration, a known marker, and color reactant to check ?) I'm just trying to learn not nit pick your post.

Also I think what the OP is asking if the TBN is not being depleted is the TBN not protecting the engine as well as the TBN being depleted... another words does the TBN have to be in depletion mode to protect.

 

[postjeeprcr]

TBN does not protect the engine. TBN itself is not an additive, it is a measurement of the amount of active additive left in the oil. I have read that the TBN measures amount of, I believe, calcium sulfonate in the oil, but don't quote me on that.

 

[Ausfahrt]

Originally Posted By: rclint


Also I think what the OP is asking if the TBN is not being depleted is the TBN not protecting the engine as well as the TBN being depleted... another words does the TBN have to be in depletion mode to protect.



I have noticed that Blackstone will recommend longer OCI's based on the TBN remaining at an oil change. On the surface this seems to imply that an oil that retains a higher TBN is better than an oil that does not. But what if the opposite is true?

I don't know the answer. Thats why I threw it out there.


Carry on.

 

[Nick R]

TBN is essentially like the oils "gas tank" of detergent additives. Whether the "tank" is full, or is only 1/16 of a tank doesn't make a difference. It's when it runs out that it becomes a problem.

 

[Jax_RX8]

Originally Posted By: postjeeprcr
TBN does not protect the engine. TBN itself is not an additive, it is a measurement of the amount of active additive left in the oil. I have read that the TBN measures amount of, I believe, calcium sulfonate in the oil, but don't quote me on that.


TBN is the Total Base Number.

Base neutralizes Acids formed through the combustion process. These acids, if not neutralized cause corrosion of all the metals part in the engine.

Also, once the TBN is used up, the oil will oxidize much quicker from the increased acidity which will contribute to the formation of sludge/deposits in the engine

TBN has nothing to do with engine "protection" - but, if the TBN runs out during an OCI, then the additional metal corrosion will cause increased wear and quicker oil oxidation will cause deposits.

There is more to TBN than Calcium - every ingredient with antioxidant properties contributes to total TBN - Calcium, Magnesium, Boron, ZDDP to name a few.

 

[slider]

TBN is a measurement of the reserve akalinity in the oil.

Different oils have different retention rates and a single data point does not provide much information except for that particular case. In this example, the oil with the lower number may stabilize for a period of time, while the one with the higher number could continue to deplete and end up lower at a later time.

The test also isn't very accurate so determining a "cutoff point" should be conservative in approach. (IOW, it's "semi-quantitative") There are also different methods (standards) that result in different numbers for the same fluid condition and one has to learn the relationships between the standards.

For example, Blackstone's method has a cutoff of 1.0, whereas for most other labs, which these days usually use ASTM D4739 it's 2.0, but some use D2896, which shows a number 1.5-2.0 points higher. For the Dexil kits, (ASTM 5894-96) which I have used it's usually considered to be 4.0 or even higher. From what I have been able to tell, Blackstone's method is proprietary and doesn't have an ASTM standard, but somebody please correct me if I'm wrong.

See how confusing this all gets?

 

[Quattro Pete]

In addition, some labs also observe the relation between TBN and TAN to determine if the oil should be changed (if TAN was tested).

For example, according to Wearcheck, their general rule of thumb is when TAN is 80% of TBN, the oil should be changed. By the way, they use ASTM D2896.

 

[ARCOgraphite]

Using and oil with the LOWEST TBN detergent contribution will allow less surface competion for EP AW agents and provide better high load boundary lubrication, smoother ioperation and less wear. So go for the lowest Ca and Mg % for your intended OC interval. Running a long drain, high TBN oil in short drain OCi is not beneficial and may be detrimental.

 

[Ausfahrt]

Originally Posted By: Jax_RX8
Originally Posted By: postjeeprcr
TBN does not protect the engine. TBN itself is not an additive, it is a measurement of the amount of active additive left in the oil. I have read that the TBN measures amount of, I believe, calcium sulfonate in the oil, but don't quote me on that.


TBN is the Total Base Number.

Base neutralizes Acids formed through the combustion process. These acids, if not neutralized cause corrosion of all the metals part in the engine.

Also, once the TBN is used up, the oil will oxidize much quicker from the increased acidity which will contribute to the formation of sludge/deposits in the engine

TBN has nothing to do with engine "protection" - but, if the TBN runs out during an OCI, then the additional metal corrosion will cause increased wear and quicker oil oxidation will cause deposits.

There is more to TBN than Calcium - every ingredient with antioxidant properties contributes to total TBN - Calcium, Magnesium, Boron, ZDDP to name a few.


I think that I am finally starting to get my head around this one. Base as in caustic or alkaline....not base stock.

Thanks for the replies, fellas. I may not be the sharpest tool in the shed but at least I'm steady.

 

[Ausfahrt]

Originally Posted By: ARCOgraphite
Using and oil with the LOWEST TBN detergent contribution will allow less surface competion for EP AW agents and provide better high load boundary lubrication, smoother ioperation and less wear. So go for the lowest Ca and Mg % for your intended OC interval. Running a long drain, high TBN oil in short drain OCi is not beneficial and may be detrimental.


Thanks.

I have no idea what you are talking about but the "high load boundary lubrication" part sounds pretty serious.