[2.2 Straight six]

head down to your local plumbing supplies store.

there's stuff called plumbing tape (also known as teflon tape) which is like thin white tape, it's used for sealing piping threads against leaks (in fact, i used some only last week)

you wrap a bit of it (enough to go around the thread 2-3 times) around the thread of the plug, and screw it in. it makes a better seal between tap thread and die thread.

this is just a quick fix, to do the job properly you'll need to either cut a new thread (it'll have to be bigger than the existing one) and make/buy a new plug or you'll have to weld up the leaking drain hole, drill a new one and weld on a new bung.