The worst of being around autos in a quarter century was on a 93 Accord where the lady had not changed the oil since she rolled off the lot, this with close to 65,000 miles on it. She was from Vermont and had $$$, she gave it to my friend's neighbor, her nephew, who was going off to college. Couldn't even get anything to come out the drain plug initially. Had to heat up the pan with mapp gas, then a little roll came out. Ultimately had to drop the pan and the sludge was caked on to the bottom of the pan, think roofing caulk. The oil pickup was amazingly not blocked up fully. The guy cleaned out the bottom of the pan, took off the valve covers, cleaned out the top end, mixed Havoline oil and a quart of ATF for every 1000 miles for five or six times. It got him through four years of college. The Japanese don't build them like that anymore.
Dated a girl who in 40,000 miles never changed her oil once in her 99 Civic. When I changed it the oil was thick as molasses and the amount that drained could only fill half of a Solo red cup. Not a keeper in my books.