Not the first time I've posted this, but . . . sometimes, an OVERSIZE OIL DRAIN PLUG offers a permanent fix to stripped sump threads.
The tapered, self-tapping slightly-larger diameter oversize plugs essentially re-tap the oil drain hole upon first insertion.
If the oversize plug doesn't seal, then . . . look to drilling-and-tapping/insert/welding and re-threading/etc. Worst case, trick "temporary" plug, like an expandable motorboat transom plug, flapper, etc. A proper oversize plug costs maybe $ 3 or so; M12-1.5 oversize plugs available from the Internet; MAY be on-the-shelf at your friendly local auto parts store. M12-1.25 more common, and may even work. I'd favor chancing M12-1.5, in hopes of rehabilitating the original threads.
DISCLAIMER: No offense intended toward those who run, screaming, from the room at the thought of an oversize plug (vs. other remedies). I've had "miracle cures" with them, and . . . factories are working nights manufacturing them; some successful application and use must come from oversize oil drain plugs.
Ain't never tried it, but . . . drilling-and-tapping for a 1/2" replacement plug might work; a 1/2" diameter might be just slightly larger than the stock 12 mm hole . . .
Last edited by Damocles; 04-29-2017 at 04:42 AM.