I don’t remember this but somewhere around that time they had a 15,000 mile oil that l remember.In the mid- to late '70s, STP marketed an oil they claimed could go 50,000 miles between changes. Really. It was 10W-50, though I'm not sure about that. I used to see it at K-Mart, but never tried it -- even as a new driver, I didn't think any oil could go even 10k miles, let alone 50K.
That was it. 50K sounds like something no consumer would believe. 15K was not *completely* beyond credibility.I don’t remember this but somewhere around that time they had a 15,000 mile oil that l remember.