My aunt had a Cougar which had 52,000 miles on it and the oil had only been changed once! She lived away and didn't know any better. When she moved back and I got my hands on the car I changed the oil. It came out as thin as black water. I put new oil in it and checked the dipstick. The new oil looked like it had 5k on it already. Over the years I took care of the oil changes and the engine never seemed to knock or tap. She sold it a few years ago. The original oil must have been Pennzoil dino because it had a Pennzoil filter on it from a Jiffy Lube. I think it shows Pennzoil is a decent quality oil. I wish I'd known about oil analysis back then. I bet it would have been horrible. I also know of a guy who bought a new Dodge truck and never changed the oil once and the engine blew at 57,000 miles. The guy actually thought Chrysler should replace the engine for free!