"Old school" stuff. We used to pour in a quart of kerosene, ATF or diesel just before we did an oil change. We'd run the car/truck/tractor around the block and then drain the oil. Just makes the oil a little thinner and quicker to drain. Never seemed to do any harm and I doubt it ever did any good but "ol' Herbie", who lives over there on yonder hill, who has been working on engines since Barney Oldfield days, swears by it.

Probably a hangover from the pre '50's cars which didn't have oil filters.