vanmanpdx

I have a 2005 Chevy Express 3500, 6L, extended body cargo van. I took delivery of it new in November 2004 and it now has 67,800 miles on it. I mostly drive around town and I treat it like a full baby stroller.

It has been 3,700 miles since my last oil change. Yesterday when checking the oil I discovered that it was one quart low. It bought a quart of 5-30 Pennzoil and that brought it nearly to the top of the full mark on the dipstick.

My question is: With only 67,800 miles on the vehicle, it isn't possible that it is burning oil, is it? If not, what could be the cause of the low oil level?

Also, how long do most of you guys go between oil changes on this type of van and what brand/type/weight of oil do you use?

Thanks.