Mobil 1 SN - TBN & Extended Drains

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Just wanted to share a response from ExxonMobil concerning their TBN levels for extended drains. This was a response from them after a question to them via their Facebook page. They bring up a point that I had never considered - if the detergent is "over-based" enough to do the job, a lower starting level is sufficient.
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"Thanks for your message, Mike. We appreciate the feedback. A slight reduction in ash is desirable for advanced engine technology such as gasoline direct injection (GDI) engine and passenger car diesel engines. With GDI engines, higher levels of ash appear to result in a higher occurrence of Low Speed Pre-Ignition. The industry is currently developing tests and specifications to address Low Speed Pre-Ignition. In the future, passenger car engine oil specifications such as ILSAC GF-6 and dexos1 (next generation) are likely to have requirements such as lower ash to address Low Speed Pre-Ignition. As for TBN retention, it is only a single parameter that provides an indication of the used oil condition. A reduction in TBN is an indication that the overbased detergent is doing its job by neutralizing acids that form as a result of combustion. TBN should be used in combination with other used oil parameters such as oxidation, nitration, TAN (Total Acid Number), ICP metals, D4684 MRV viscosity, and D445 kinematic viscosity to determine the overall condition of the used oil. Finally, in our experience in severe-service Las Vegas field testing, Mobil 1 engine oil TBN levels typically do not drop below 2 for vehicles with 15,000 mile oil drain intervals. Furthermore, it is our experience that those oils tend not to drop any lower when we continue to 20,000 mile oil drains. We hope this information was both helpful and informative. Thanks again for reaching out, and for your continued support of Mobil 1."
Additionally, there is info online about Mobil 1 being used in NH municipal fleets for 15,000 mile drains per ExxonMobil's recommendation. So, perhaps Mobil 1 is a better long drain oil than we realize and/or are willing to test the limits of?
 
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The Critic, Thanks very much for posting this - would love to have seen the exact original question. However, I interpret their response a bit differently than you. Taking their statements one at a time:
Quote:
A slight reduction in ash is desirable for advanced engine technology such as gasoline direct injection (GDI) engine and passenger car diesel engines. With GDI engines, higher levels of ash appear to result in a higher occurrence of Low Speed Pre-Ignition. The industry is currently developing tests and specifications to address Low Speed Pre-Ignition. In the future, passenger car engine oil specifications such as ILSAC GF-6 and dexos1 (next generation) are likely to have requirements such as lower ash to address Low Speed Pre-Ignition.
Got it. Lower sulphated ash is the future - most likely all GF-6 oils will have lower SA levels.
Quote:
A reduction in TBN is an indication that the overbased detergent is doing its job by neutralizing acids that form as a result of combustion.
I interpret this to mean that it is normal for the TBN to decline as the interval progresses, not that a lower starting TBN in a VOA is sufficient.
Quote:
TBN should be used in combination with other used oil parameters such as oxidation, nitration, TAN (Total Acid Number), ICP metals, D4684 MRV viscosity, and D445 kinematic viscosity to determine the overall condition of the used oil.
Agreed. I have begun having both TBN and TAN tests performed. I wish Blackstone would offer oxidation and nitration, but they do not. I know other labs do, but Blackstone is so much more convenient to use, and I have a lot of trending data accumulated with them.
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Finally, in our experience in severe-service Las Vegas field testing, Mobil 1 engine oil TBN levels typically do not drop below 2 for vehicles with 15,000 mile oil drain intervals. Furthermore, it is our experience that those oils tend not to drop any lower when we continue to 20,000 mile oil drains.
I also have never personally experienced a TBN lower than 2 on any run of Mobil 1, even to the 10K mile mark. I guess my question is how close can you get to Blackstone's condemnation level of 1.0 before bad things start to happen? I like to have some margin of safety. As I have mentioned on other posts in this forum, I have become a bit concerned about Mobil 1's TBN retention since they have switched to their new SN formulation. I am now planning to try Amsoil's signature series to compare TBN retention. This question/response you have reported is exactly the same as my concerns that I have noted in this forum, so apparently, others have noticed and are concerned as well.
 
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Originally Posted By: The Critic
Just wanted to share a response from ExxonMobil concerning their TBN levels for extended drains. This was a response from them after a question to them via their Facebook page. They bring up a point that I had never considered - if the detergent is "over-based" enough to do the job, a lower starting level is sufficient.
Doesn't an overbased detergent contribute to the initial TBN??
 
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I get what you're saying: Once the initial TBN get depleted to a certain point, the detergents themselves begin to neutralize the acids, thus preserving the TBN. That would also lower the initial TBN but increase TBN retention. Am I getting closer??
 
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JHZR2

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Originally Posted By: Gabe
Originally Posted By: The Critic
Just wanted to share a response from ExxonMobil concerning their TBN levels for extended drains. This was a response from them after a question to them via their Facebook page. They bring up a point that I had never considered - if the detergent is "over-based" enough to do the job, a lower starting level is sufficient.
Doesn't an overbased detergent contribute to the initial TBN??
I would think so. I don't think a TBN titration would discern basicity from the add pack as detergent vs buffering agent vs anything else. I have seen TBN < 2 in 5k ocis on their VW 504/507 oil, though one could argue that it is the wrong application...
 
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Reading other oil manufacturer responses on here, they are usually vague and ambiguous. XOM gets high marks for such a detailed response.
 
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btanchors, First of all, I want to commend you on your analytical and organization skills. Between you and 2010 FX4 you guys have it down. smile I guess my thoughts concerning Mobil 1 SN oils is this: I think the TBN depletion curve is different than the SM variant. Not inferior, just different. I believe the Ca/Mg combo drops to 2.0 TBN quicker then slows down before 1.0 is reached. I think the old SM behavior with the high Ca levels gives a slower drop to 2, but maybe not to 1.0 TBN. PP & PU probably exhibit this depletion pattern. I would bet anything that if BiTOG was privy to the internal documentation during Mobil 1 EP long term testing, we would see the TBN near or even below 1.0 after 15000-20000 miles. I believe any ultra long (>12,500 miles) OCI with a low Ca formulation will have the TBN nearing or below 2.0 (Blackstone). TAN and/or oxidation and Nitration values will need to be considered as the TBN nears 1.0 in order to most accurately assess the condition and suitability of the oil for continued usage. Allowing the TBN to dip below 1.5 is needed to get past 15000 miles OCI in most cases. This will separate the men from the boys!! I look forward to your testing. I will be switching to Mobil1 EP soon and start the extended oil testing drill. Take care, Gary
 
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Tucson - Many thanks for your comments. If I had more money and time, I would go a lot further with this, believe me...I love doing these types of experiments and comparisons. Too bad I could buy a few engines and test stands, and do some real testing in a lab setting!
 

The Critic

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Originally Posted By: Gabe
Originally Posted By: The Critic
Just wanted to share a response from ExxonMobil concerning their TBN levels for extended drains. This was a response from them after a question to them via their Facebook page. They bring up a point that I had never considered - if the detergent is "over-based" enough to do the job, a lower starting level is sufficient.
Doesn't an overbased detergent contribute to the initial TBN??
I am not sure. It is possible that my interpretation was incorrect. Btanchors, great job as usual with your analysis.
 
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Quote:
This is one reason why higher levels of TBN’s can mislead you into thinking it is better when in fact all it is stating is that it has higher levels of detergents to keep the engine clean but the base oil can oxidize(or breakdown) faster than one with higher levels of antioxidants which prevents the acids by neutralizing the attacking acids as oppose to cleaning up the by products of the oxidized oil.
Another interesting point. Remember that some oils have high starting TBN's but that does not mean they are necessarily BETTER for longer drains. Remember the old Amsoil formulations? Very high TBN's but would thicken out of grade. They have corrected this now, but it kind of relates to this topic.
 
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Buster, M1 oils not oxidizing has been my observation with M1 oils all along. Many here seem to think TBN is the WHOLE thing with oil and extended drains. That's wrong. Staying in grade is one reason M1 oils keep engines very clean for high miles. Some think varnish is OK, but that is caused from the oil oxidizing and is an indicator that ring coking may occur. A superior base stock is vital in preventing this.
 
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Originally Posted By: tribocessive
vegas taxi oci's to 20k with M1? that's interesting; they are the prime candidates for shorter oci's in the old way of thinking.
In many ways they shouldn't be, as the oil often never gets cold in most taxis...
 

Bill in Utah

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Finally, in our experience in severe-service Las Vegas field testing, Mobil 1 engine oil TBN levels typically do not drop below 2 for vehicles with 15,000 mile oil drain intervals. Furthermore, it is our experience that those oils tend not to drop any lower when we continue to 20,000 mile oil drains.
Nothing in the Mobil 1 Las Vegas test is "severe". Then why did they not run out to 20k OCIs? Why don't they recommend 20k OCIs and warranty that? (if Las Vegas is so severe and the normal owner is not?) Marketing is so great.... slobber
 
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Of course it's severe. Running in the heat, idling and just going 15k miles on any oil is severe. What a ridiculous comment. Why not 20k? Probably to give them a cushion or, wear is not controlled as well at that point. Tbn, as they said, is not the only indicator of oil quality.
 
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Originally Posted By: Bill in Utah
Then why did they not run out to 20k OCIs?
If I got 6,000 miles out of QS conventional for $1 a quart back then in the cabs, I'd have needed at least 30,000 miles out of M1 for the $5+ a quart to make it worth it.
 
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