the lug nut is probably the best idea in here. I havenīt thought of that before (probably because I donīt have a bunch of lug nuts lying around)
the hammer and chisel is only ment if your fill plug is so damaged (by using the wrong tools on it) that you canīt get a normal socket on there i have sometime banged an 23 mm socket on these nuts after having a bad luck with the other one... but again. welding a lug nut is probably the easyest at least on those diff drain plugs
