An off-the shelf dino oil, 4000, maybe 5000 miles max-then only w/oil analysis.
Most ots blends, same as above.
Ots Synthetics, no more than 8,000 to 10,000 miles, ditto.
"Special" oils"? I now have over 8900 miles on the Schaeffer blend in my car- plan to change it this weekend at 9000 miles if weather permits. I won't panic if I have to leave it in for an extra 600 miles or so. I base this on the results of my last analysis at 6000 miles. The Schaeffer dino-moly? I'd be willing to run it at least the 7,500 miles my owners manual recommends for light service, *without* doing analysis, based on my results with their very similar blend. Amsoil? I have no experience with it, but it seems to be better than M1, I might gouyp to 12,000 miles or so with analysis.