GC weak TBN?

[another Todd]

I've just been reading some UOAs and it seems GC TBN seems low for extended drains like I perform. Usually my Oil Life Monitors direct me to change oil around 9000 miles. And I do a fair amount of short trips. What do you think of mixing GC with rotella synthetic 5w-40 50/50 to raise the TBN? Good/Bad?

 

[ekpolk]

How do you define "weak" and what's "extended" for you? What vehicle and engine combo are you talking about? All these will bear upon the ultimate answer. I've used GC as long as 10k miles, and not had a TBN problem. Keep in mind that Blackstone TBNs, seen often here, tend to be lower than those from other labs. I would not mix oils for a longer drain run. You're experimenting in uncharted territory at that point. Can you cite a couple of the examples that concern you? With that info, we can answer your questions in a more meaningful way. My longest example, 10k miles in 13 months, good TBN, (posted in UOA section) may be unfair in the other direction, as it was in my wife's 4.7L Toyota V-8, an engine that seems to do nothing at all to oil. OTOH, a sick or hard-on-oil engine is going to torture whatever you put in it. GIGO, more info = better discussion.

 

[another Todd]

By extended drain I mean approx. 10,000 miles/ 1 year. However, my driving habits tend to put me in the severe service category ie. short trips etc. Engines/vehicles include 2000 Silverado 4.8 V8, 99 Cherokee 4.0 I6, 05 Trailblazer 4.2? I6. It seemed in reading the UOAs, that after 5,000 miles many were in the "2 to 4" range which seems low to me, if I were going to double that mileage.

 

[ekpolk]

Remember, the decline in TBN is generally not linear. I had a 2.6 TBN after 7100 miles in my G35. In the Sequoia UOA I mentioned above, it was 3.0 after 13 months and 10k miles of mostly short tripping (2-3 miles). In the end, the only way you'll know for sure is to test your vehicle under your usage circumstances. You could run it to 5-7k miles, test, extend from there as appropriate to your predicted max OCI, minus a safety margin, then test again to confirm. You wouldn't have to do this every OCI, but this is how to know for sure for your situation. I'd also highly recommend a consult with Terry Dyson. I am a several year, very satisfied customer, and would recommend his service without hesitation.

 

[ekpolk]

Oh, a couple more thoughts. First, especially with Blackstone, the 2-4 range is not really low. It's getting there, but not by any means finished. If you have not already, I'd pick through the UOA section with special emphasis on those vehicles. The Trailblazer, with its oceanic oil volume, should be a relatively easy longer OCI case.

 

[another Todd]

Is there a way (additive) that will increase TBN only? Or TBN plus some other benifet?

 

[Titan]

Quote:

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Is there a way (additive) that will increase TBN only? Or TBN plus some other benifet?

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You mean like, perhaps, Lube Control?

 

[JAG]

TBN is just one thing that must be okay. An oil can have enough TBN and still need to be drained due to other reasons: contending with high moisture or fuel content, oxidation, nitration, high insolubles, overloaded dispersants, or high TAN. Those things can cause engine sludge or varnish and in the case of high TAN, corrosion. Oils that can "fail" before TBN is shot are mineral HDEOs used in gas engines because they have very high TBN but not as good chemical change resistance as most passenger car motor oil synthetics.

GC has quite good TBN retention and very good resistance to breakdown. If it can't do what you want it to, it's because you are asking a heck of a lot from it. Use it and start doing UOAs to see how long it lasts in your applications. Mobil 1 0W-40 is another long drain oil that may work well for you.

 

[paul_e320]

If Blackstone's TBN readings are lower than other labs, does that mean they're more accurate or less accurate? I can understand that different testing methods/apparatus can yield different results, but doesn't ASTM D2896 dictate this?

Regards,
paul....