I change oil in my work trucks every 15K miles. They hold 44 qts.

My F-450 diesels get's changed changed every 12K miles, they hold 15 qts.

My pickup trucks and cars get's changed every 10K miles.

Been changing oil now since 1984 and have never had a engine failure. We do use a top quality oil (Amoco600) I also have built many motors from scratch. OH yea, everything I own get's 15-40, lawn mowers and all.

Changing OIL EVERY 3-5k MILES is a waste of money, I maintain more than 20 vehicles for 25+ years now. I know from experience, not from what someone says.