Just pulled the cover off the head of my 01 PT Cruiser. It has been run on Mobil 1 5W-20 for most of its life until I switched to 0W-40 last year. With the 0W-40 it used significantly less oil. To my pleasant surprise the head look clean as a whistle; no sludge anywhere. The cams are in excellent condition. By the way, I have always changed the oil and filter just once each year without regard to distance driven. I live in upstate NY so it gets very cold and very hot during the year.