TBN graph - is this a good way to look at OCI?

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I have been plotting my TBN data with OCI and used the "0" data from Liquimoly's product data sheet (I'll get an analysis on virgin oil next oil change). Is this a reasonable to look at how long you can push your OCI? Blackstone is saying on my last UOA to go to 9K - I'd say looking at this graph that makes good sense. Finally, what TBN is the bottom threshold for "change it"? Thanks!

TBN.JPG
 
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No because some cars are harder on oil that others along with driving conditions that come into play. But wouldn't it be nice. Get a UOA.
 
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No, TBN is not linear. Depending on what is going on in your engine and the oil you're using, TBN usually takes a steep dive shortly after being placed in service, and then begins to become semi-asymptotic, but will obviously hit zero at some point. Some oils may drop from 10.0 to 4.0 in the first 2k miles, and then still be >2 @ 7500 miles. IMO there are only a couple things to look at on a UOA which can give you this- and the main two are: did the oil remain in grade during its service life, and is TBN still >1? Another "umbrella" limit would be 150ppm iron.... say you were really extending your OCIs and topping off as needed so TBN was fresh and viscosity maintained- if your UOA shows greater than 150ppm Fe it needs to be changed since the oil is becoming very abrasive at this point. Other than those two things, how an oil reacts during an OCI is too variable. Trend your wear metals and watch for spikes (>50ppm increases) but do not worry about changes in wear metals if they are single digit increases- nothing has really changed in your engine.
 
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Originally Posted by Donald
Your graph shows it to be linear but its not. Something is wrong.
Looks like a sample size of 3. Needs more data. However Blackstone's recommendation to go to 9k seems solid, especially if the UOA showed that there was no degradation of the oil (as in fuel dilution or thickening) OP, what oil and what vehicle are we talking about here? Opinions on when to change based on TBN vary from member to member and oil analyzer to oil analyzer. Mine is 1.5 (going conservative on Blackstone's 1.0) but I have never reached that number, as all of my extended OCIs have been with Amsoil.
 
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TBN is interesting and worth testing for. But TBN by itself tells you little about other oil qualities. In many of today's engines, particulates, viscosity (shear) and fuel dilution are the key issues. Especially as the viscosity of the base oil is already very low. Consider the Honda 1.5L turbo engine, with fuel dilution and subsequent rising oil level problems. The TBN can easily be well within the acceptable range and the oil can be unable to protect properly.
 
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TBN is almost linear, at least at first, then usually plateaus off and drops more slowly. More like 2.7182818284590452353602874713527 ^ (-constant x miles) in shape. 1.0 is about the worst it should ever get before changing oil. Past that, and acids don't get neutralized properly. Other factors do complicate this. Lots of short trips and Cujet's fuel dilution indeed overwhelm buffering, especially when TBN is below around 3. https://media.noria.com/sites/archive_images/Backup_199901_Graphics_GM4.gif https://www.machinerylubrication.com/Read/77/gm's-oil-life-system-improves-timing-of-oil-change
 
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oil is relatively cheap, even fake synthetics as most are. unless all long trips 5,000 intervals is best + just forget the overrated oil analysis IMO
 
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Originally Posted by benjy
oil is relatively cheap, even fake synthetics as most are. unless all long trips 5,000 intervals is best + just forget the overrated oil analysis IMO
I agree, most of the people in here change their oil far to early, and ignore the labs recommendations, and your engine is always wearing metals, And then people start stressing if they see one number off they over analyze it. Pay attention to your driving habits during oci, know your cars characteristics I.e d.i for fuel and go from there. Then people say they are on a budget for oil, yet paying x amount for uoa. Save the money from the uoa buy a full synthetic, and change at 5-7k. Check your filter or cut it open from time to time. Only time I have ever done them, after purchasing a used vehicle, or if new done one at 75-80k. Pay for the best oil possible instead of someone who's advice you probably still won't follow anyway.
 
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Blackstone always says to change the oil at 1.0 TBN. Polaris uses a different ASTM method to measure TBN, and recommends changing it at 35% of virgin.
 
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Originally Posted by JohnnyJohnson
No because some cars are harder on oil that others along with driving conditions that come into play. But wouldn't it be nice. Get a UOA.
I did/do...that's where the data came from...
 
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Originally Posted by Donald
Your graph shows it to be linear but its not. Something is wrong.
Just a trend line I added - I also only have a few points....just a discussion piece really.
 
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Originally Posted by JLTD
Originally Posted by Donald
Your graph shows it to be linear but its not. Something is wrong.
Looks like a sample size of 3. Needs more data. However Blackstone's recommendation to go to 9k seems solid, especially if the UOA showed that there was no degradation of the oil (as in fuel dilution or thickening) OP, what oil and what vehicle are we talking about here? Opinions on when to change based on TBN vary from member to member and oil analyzer to oil analyzer. Mine is 1.5 (going conservative on Blackstone's 1.0) but I have never reached that number, as all of my extended OCIs have been with Amsoil.
Thanks. This is my 2018 VW Golf Sportwagen with the 1.8 - it does have performance modifications for significantly more power than stock. Oil is Lquimoly Leichtlauf High Tech 5W40. I will be collecting more data just wanted to get some convo on this going.
 
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Originally Posted by domer10
Originally Posted by benjy
oil is relatively cheap, even fake synthetics as most are. unless all long trips 5,000 intervals is best + just forget the overrated oil analysis IMO
I agree, most of the people in here change their oil far to early, and ignore the labs recommendations, and your engine is always wearing metals, And then people start stressing if they see one number off they over analyze it. Pay attention to your driving habits during oci, know your cars characteristics I.e d.i for fuel and go from there. Then people say they are on a budget for oil, yet paying x amount for uoa. Save the money from the uoa buy a full synthetic, and change at 5-7k. Check your filter or cut it open from time to time. Only time I have ever done them, after purchasing a used vehicle, or if new done one at 75-80k. Pay for the best oil possible instead of someone who's advice you probably still won't follow anyway.
I have been doing mine at ~7-7.5K and that's a good spot for me...matches with tire rotation schedule and mostly highway use. The issue is my car is tuned and making significantly more power than stock at this point. The UOAs seem to show it's just fine (should be...I don't launch it 10x a day or track it) and I was just curious if the Liquimoly would hold up to the full 10K VW recommended interval; my data suggest it will and 9K recommendation from BS will be worth testing...probably will be fine and show 10K is also fine but in the end, 7.5K is where I will land and UOA data I have so far supports it.

18 GOLF SW-191005_UOA_21K.jpg
 
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Here are my updated data. Seems like 7.5K is a good interval for me - plenty of TBN and viscosity is just below 40W. I had virgin analysis done so have a true "zero" number to start and pushed my last change to 9K to see how the oil held up.

oil_data_graphs.JPG
 
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