I can just imagine the owners previous mid-oil change dialog playing out in his mind 2 ways:
" Ok...oil is all drained out, just need to wipe the opening and put the drain plug back in.....wait a tick, where is the drain plug?!!? "
(looks around for 30 mins)
" @#$%&, cant' find the @#^&@ drain plug !!! "
" Well, I have to get to work, what can I use instead ?!? "
(tries various loose bolts with no success, spots some old broken part at the bottom of the bin)
" I wonder if that old broken spark plug will fit. "
(tries it on by hand and it fits)
" Huh...would ya look at that...but I am worried oil will leak out the broken end...how can I plug that ?! "
(looks around for various candidates....finally spots an old rivet)
" I guess you will have to do "
(jams rivet into the spark plug)
Next OCI rolls around...
" oh yeah, the spark plug, hehe, I'll take it in and maybe score a free drain plug, cuz I am too cheap and stupid to get my own. "
Or
$25...for a drain valve !?! ..... Forget you Fumoto, I'll make my OWN drain valve !