Just to put a period on this thread, the 7 dollar oil pressure switch arrived last night so I put it on and that stopped all leaking. I laid under the truck for twenty minutes, with it running, watching for the slightest drip, wiped it down everywhere like an insane person, and then slept like a baby.

I never knew that an oil pressure switch could leak out of the top of it. But if there is a way to leak, a rover will find it.

I'm running out of things to fix and know the sizes of bolts without even glancing at them. A major breakdown is surely coming...