Originally Posted By: pioneer
I have always wondered if the 3 month recommendation was clever marketing years ago that has turned into "fact".
Some of it, yes. I believe it was Jiffy Lube who coined the 3 months or 3,000 miles mantra, back in the early 1960s (I did a report on this for work a while ago, and I don't recall the exact date). Anyway, sure, they were trying to get business.
But on the other side of that, yesterday's oils were very crude, so to speak, compared with today's oils. Sludge was not uncommon, even in "well-maintained" engines. Yesterday's engines, also, were much harder on oil than today's engines are, what with straight-cut gears in the oil pumps, solid lifter and flat tappet valvetrains, etc.
Today's oils are much better, and today's engines are much easier on oil.