1924 Chevy manual says "Always use the best oil as it is more economical in the long run." The hand waving ambiguity alluding to expensive rather than most suitable product specifications. It's good to hear that consumer propaganda wasn't a recent invention.

By the way, here's some service-writer lingo: eyewash n. - Customer impressive procedures or checks that either not performed or are a required step in the course of a job used to make it seem more valuable.