Before the 1990s, we used to change CD- and CE-classified diesel oils every 8,000 to 12,000 miles in Class 7 and 8 trucks, and more often for smaller ones. We did "dry" maintenance (chassis lubrication only) halfway between "wet" intervals. Since then, we've had to adjust such routines to keep up with advances in engine oils and truck technology. Most improvements in oil formulations have followed changes in emissions regulations. While refiners continually upgrade their products to remain competitive, the establishment of new standards is what drives real progress.
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