I have four vehicles in my care, two of which I keep on 3K OCI.
'97 wrangler 4.0L - It's had Mobil 1 since the first oil change every 3K and it runs like new......which is crappy, but not much I can do about it. I keep it on 3K intervals because it sees only short trip driving, 10 minutes 2-3 miles is very common.
'01 SAAB 9-5 Aero - This has been on and off of mobil 1 depending on where the oil was changed. I keep this on 3K intervals for 2 reasons. 1. It has a flawed oil pump and pcv system that makes it prone to sludging and lose oil pressure when wear occurs. 2. It sees no highway miles, 40 mile commutes 5 days a week, and I tend to drive the bejesus out it.
If I buy the oil at Walmart, it's cheap insurance. I don't care much about the jeep, but it'd be more of a hassle to replace it. I looooove the saab, and I'll do anything to keep my baby. Plus it's only about 3 changes a year, no biggy. That's about $75 a year in filters and oil, cheap insurance indeed.