DO you honestly think you are the only mechanic on the forum, get off your high horse. Whenever i rebuild a diesel, i run kero through it for 15 min 1500rpm free rev, obviously you dont rebuild diesels otherwise you would do the same.
To the OP i would drain the oil, and refill with 50%cheap oil, 50%kero and run it for a few min then drain it while it is hot. If you are worried about the bores being rusty, then you are up for a rebuild anyway, so might as well give it a go..