This is not another oil thread, just a question if anyone else had used it. The truck in question is a 1990 Kenworth with a Cat engine and 600,000+ miles. If he says he can tell a difference between Mystic and Rotella (in a good way) then it is better. One difference is the Rotella is 15/40 and the Mystic is 15/50. That could be what made it feel different. The Mystic is a simi-syn, diesel rated oil and will go in my 300D at the next oil change.
Paul

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84 500 SEL (307,xxx miles)