Different oils provide different levels of protection
How many miles should an oil last? Here we can see different oils in similar trucks that run the same routes and loads. These samples are from 2001, before the introduction of CI-4 diesel oils.
In sample 180878 (marked in yellow) we have a 15W-40 "Made in Bolivia" that in theory was a CF-4. At 6,000 kilometers it had less than 20% of the detergent/dispersant needed and 25% of the anti-desgaste additives needed to avoid problems in the engine. The TBN is so low that it will not fight acid build up, and the viscosity has dropped to a SAE 30.
Three weeks later, with 4750 km running a CH-4, the oil was analyzed and although it was still cleaning up the mess left behind, it showed better results.
The next sample is another Bolivian oil with 11,000 km in one of the same trucks. When we compare this sample to the others below we can see that with 11,000 km, it has more wear and less additives than the other oil at 15,000 km.