I had a 1986 Toyota truck with a 4 cylinder engine. I believe the recomended
oil change interval was 7500 miles. This was a work truck that hauled material and tools everywhere it went. LA stop and go traffic to wide open fwy driving. I owned that truck for 14 years and logged atleast 300K miles on it. I was never anal about the
oil changes. I did use Castrol non-
synthetic 20-40 and tried to stay on top of the scheduled changes but would let the miles between changes sometimes go 10, 12 or 15K miles and sometimes even running low. The truck was still running strong when I sold it. Never had an internal engine failure while it was mine. Brakes, clutches and alternaters yes but the truck ran like a champ. I never worried too much about it and wonder how much of the 3000 mile
oil change is a marketing ploy of our oil companies and service centers to sell more oil and get your car in for services.
John