2022 Corolla Cross HPL PP 0W-8 30k mi OCI

So high TBN value after 30k is interesting. Is that somehow related to low oil dilution? Do you use regular gasoline or some premium (Top Tier in the US?) What is your driving style and how is the car used - how many cold starts for 100 miles, etc.? There is a big difference if this is a daily commuter or long-distance courier service.
Anyway - amazing results.
 
A great example of a high quality oil under relatively low stress conditions. If I remember correctly this vehicle is used for some sort of deliveries in California? Lots of miles put on with few cold starts.

Not knocking anything but it's likely not feasible for me to run 30k miles with 5 mile runs in -20F weather. Right car, right oil, right environment = great results.
 
Wear metals look great, fuel level looks great, and TBN looks supurb.

The question I have is when the sulfation, oxidation and nitration levels are high, are those three criteria for sludge formation and varnish? I’m sure there wouldn’t be much (of that) with 89,000 miles on the unit, but longterm is that something to be concerned about?

But a 0W8 oil for 30,000 miles is very impressive!
 
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Would a potential depletion of detergents and dispersants be somehow recognizable from the UOA? I suspect that the end-of-useful-life of the oil indicated by a rise of wear metals or a drop of TBN would be too close to the end of the useful life of the motor itself.
 
Would a potential depletion of detergents and dispersants be somehow recognizable from the UOA? I suspect that the end-of-useful-life of the oil indicated by a rise of wear metals or a drop of TBN would be too close to the end of the useful life of the motor itself.
Again, paraphrasing from conversations with David: oxidative thickening into the next grade would be a condemnation point. Where TBN crosses TAN is not as relevant, but an increase of 2 full numbers over the baseline acid number is relevant, and/or TBN
With the advances in add packs and much better base oils, we are learning more and more about newer, more relevant ways to determine condemnation points rather than what was available 15-20 years ago, and the capability to easily exceed anything that would have been considered sane back then. A 30k OCI with great trends, with no makeup oil? Absurd even 5 years ago! We live in exciting times!
 
TBN and TAN only gives you a glimpse of an oil's base and acid content and is a bit of an oversimplification as far as determining oil life. They don't show the type of acids and bases, nor how corrosive and neutralizing they may be. Furthermore, the tests are geared toward mineral acids. ASTM D2896 uses perchloric acid while D4739 uses hydrochloric acid, both are mineral acids. This was great when fuels contained high amounts of sulfur and blow-by was more of an issue, but that's not the case anymore. Now we have fuels with 10% ethanol which can form corrosive organic acids. TBN does not reflect an oil's ability to neutralize organic acids. Organic acids undergo surface reactivity rather than breaking down the core like with mineral acids. This means the surface to volume ratio of detergent is more important than the total base itself. More weaker detergents is more effective than a lower amount of stronger ones when it comes to neutralizing organic acids, an important note for GDI engines susceptible to high fuel dilution.

An oil will 3000 ppm of 200 base detergent will be more effective than an oil with 1500 ppm of 400 base detergent, even though the TBN of the oil would be the same. (simplifying numbers)

Calcium based detergents are slightly more effective at neutralizing organic acids than magnesium based detergents.

This is why more tribologists and formulators (including Lake Speed Jr) consider TBN to be a bit of a dinosaur.
 
After my initial excitement has subsided I've come back here to double check again. The viscosity is in the mid 0w-20 range. The 20k samples made it into the low 20 range. IMO 20k would be the sweet spot. It's a Honda so it will live regardless.
 
After my initial excitement has subsided I've come back here to double check again. The viscosity is in the mid 0w-20 range. The 20k samples made it into the low 20 range. IMO 20k would be the sweet spot. It's a Honda so it will live regardless.
There’s no real downside (other than a slight possible change to mpg) in this case, since the engine is recommended to use Xw20 anyways. Everything else is stellar for the mileage. 30k is not doing any disservice to the OP’s engine. 👍🏻
 
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