I'm running the second of two 5000-mile intervals on PP 5W-30 in the Buick's normally-aspirated 3.8 V-6. I'd guess I do about 70% city driving, hot weather nearly all year, with a 9-mile commute one way, totaling about 850 miles/month. (There's not a lot of places to go in The Swamp, especially when it's nasty hot and you're risking damages from potholes.)
The OLM seems to count down at about 11 to 12% a month. Right now, at 5 months, it's at 47% oil life left.