It's the beater van with 170,000 miles, and I don't remember exactly how many miles it's been driven since I last changed it (somewhere between 5000-7000 miles with Pennzoil Platinum). I finally did an oil change recently and saw there was nothing on the dipstick, and what drained out was really dirty oil. It never burned oil like this before. I replaced the PCV as a start and went with high mileage oil. Should I let this oil clean out the engine for 3000 miles/6 months and then perform an oil flush with some flush chemical and cheap oil? Dirty piston oil rings perhaps? I know these 3.0's don't like short trips or extended OCI's as they are prone to sludging, and we do use it for a lot of short and long trips.