TBN of new/used engine oils - why the variation?

[TooSlick]

There are two accepted methods for determining the total base number (TBN) of engine oils. ASTM D2896 is normally used for new oils, and ASTM D4739 is normally utilized to test used engine oils. If you test the same batch of used oil using both methods, the ASTM D4739 test will yield a low number - typically 1.5-2.0 points lower, based on the results I've seen. Blackstone Labs and Oil Analyzers Inc (OAI) employ the ASTM D2896 method, for both new and used engine oils. Cleveland Tech Center (CTC) and most of the other labs I've seen like Analysts, Inc employ the ASTM D4739 test protocol, so their results for TBN of used engine oils will consistently be lower. I think you'll find that ASTM D4739 is generally used for testing of HD diesel oils in particular. I hope this helps explain this situation .... TS

 

[Patman]

The lab I use (Wearcheck in Mississauga) uses the 4739 method for TBN. I wish they didn't, as it makes my UOAs look worse than they really are. Their oxidation and nitration numbers are abnormally higher too unfortunately.

 

[Pablo]

Thanks Too Slick - "test methods", "units" and other deltas are something that needs to be perfectly clear in all the analysis forums. Indeed in my four lab comparo there is about a 1.5 point delta on TBN, so you are spot on. Back in the day we may not have known this...... One thing I will say now that I have 3 of 4 lab reports - some of these reports would get a C- at best in good old college chem. lab. No units, no test methods, and certainly no error calcs. Once again the Oil Guy site shines! [ March 08, 2003, 07:42 AM: Message edited by: Pablo ]

 

[TooSlick]

Pat, I see no issues with either method, as long as you are aware of it ....If the lab you use runs the ASTM D2896 test, I'd use a lower limit of 5-6 on TBN. If they use the ASTM D4739 method, I'd use a lower limit of 3-4 on TBN depletion. I'm just glad I figured it out ...it was driving me nuts. TooSlick

 

[BOBISTHEOILGUY]

Actually, this is one reason why you'd want to sample your oil with in 1-300 miles so to get a baseline from the company you're using, then sample at the drain interval you're wanting to check. This way, you have a starting tbn from them,regardless of what testing method is used, then you could see the drop based on your first 300 mile sample as a comparision.

 

[Patman]

quote:

---

Originally posted by BOBISTHEOILGUY: Actually, this is one reason why you'd want to sample your oil with in 1-300 miles so to get a baseline from the company you're using, then sample at the drain interval you're wanting to check. This way, you have a starting tbn from them,regardless of what testing method is used, then you could see the drop based on your first 300 mile sample as a comparision.

---

That is exactly what I did with my current oil. I took a sample at 700 miles to get a baseline, so when I'm done with it in a couple of weeks, I can get a better idea of how the oil progressed. I wish I could afford to do this on every oil change, but two UOAs for each oil change gets costly.