A while back we had a similar thread aboout when to change oil.
At that time, I mentioned that Consumer's Union ran a test on NYC taxis a few years ago, changed some at 3000 and some at 7000 or 7500. After hundreds of thousands of miles, there was little difference in wear between the 2 intervals.
Dunno what kind of oil they used but since I do LOTS of driving, it convinced me to change oil about every 7000. I use WalMart synthetic
5w-30 that is pretty cheap compared to Mobile 1 (which I used previously) and of course ALWAYS change the filter with the oil.
My Chrysler van (3.8 engine) has over 200k now and uses about a quart between changes. The Oldsmobile I drove previously (3.1 engine) had over 400k when I FINALLY gave it to my sister-in-law--it used about a half quart between changes. By the way, she is STILL driving the van, altho I'm sure it does not get the oil changed as frequently now. And tho the trans was rebuilt twice, the engine had never had more than normal maintenance.
Nor has the Chrysler.
John