2002 Buick Century
The last time that the oil was changed was in a shop (Sears). That plug is in really tight. The odd part is that I can't seem to get a wrench on it good enough. 5/8" is too big, so that an open end 5/8" wrench can move about 40 degrees or so before it locks on the plug's hex nut end. With alternatively trying a 12-pt box end wrench or a 12-pt socket, there is also enough movement that I'm afraid to crank hard on it for fear of rounding. But a 9/16" box or open end or socket is too small to even get on.
15mm seemed too big, and 14mm too small to get on.
From what little I can see using a mirror and flashlight, the plug does not look rounded.
So I tried an adjustable wrench and set it to a nice tight fit, but I can't get myself in close enough to hold my free-hand thumb on the thumb-adjuster wheel -- so when I push down hard on the wrench the jaws open a little. I did not use any kind of extension on the wrench. After two attempts like that, I quit for fear of rounding.
So what should I do? Try to find a 19/32" wrench? Would a 6-pt 5/8 socket, if I can find one, be the approach least likely to cause rounding? (I've removed drain plugs dozens of times in the past lying on the ground and using an adjustable wrench, but there was never one this difficult.) Thanks.
(Advance Auto's site is no help as to size. I suppose it's 5/8", but why would an open end wrench be loose before I even put any force at all on it?)