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What about the Chevron Delo 400? It's the same weight, but is it the same or better than the Rotella? And as far as the weight goes, is there really a big difference in the 10W and 15W?
Chevron Delo 400 LE 15W40 actually has more zinc than Shell Rotella T 15W40. I don't remember exactly, but it's above 1300 ppm zinc. At least 1200 ppm zinc is best for a flat tappet cam. I suppose 1150 ppm zinc (approximate) is OK, such as Shell's Rotella T's, for a stock engine or a mildly built engine. That's up to the individual to decide.
Shell Rotella T 5W40 full synthetic has about 1400 ppm zinc.
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