If all else fails, try an oil suction gun, available at tractor and auto supply stores.
If the corners are rounded off badly, maybe you can have someone drill it carefully and use an "easy-out" on it. This along with vise-grips, too.

Why not use a vise grips to remove it and replace with a new hex headed plug?

Either leave it alone (if it's not leaking) and dump old oil by tipping as rdaystrom said, or get a vacuum pump as rusty said (my favorite method). This will come in handy on your autos and trucks too. Later model mowers have an extended oil fill tube to avoid getting oil on the deck when tipping to dump, but yours may have the short fill housing with no dipstick. The pump really works great on these because you can actually see the bottom of the crankcase. I prop up the the hot mower on the ramp to my shed so the oil fill is at the low point, then vacuum out the oil. This is so quick and clean you'll wonder why you haven't been doing it all along.

If you're still willing, hardware stores sell a tool "socket" to remove stripped bolts. It digs into the bolt head. It has worked for me.

I had a oil drain plug on a riding mower that was very frozen. I tried wd 40 oil but later switched to an oil such as Nano penetrating lubrication to get better penetration with the lubricate. I also used a 12 to 18 inch long steel pipe that I put over the box and open wrench to provide additional leverage. It was hard to move but with both the penetrating oil and pipe leverage I was able to get the plug loosened.

??? How many oil drain plugs have you experienced fixers found, that have opposite threads from the norm? I think a lot of stripped oil plugs come from amateur mechanics who don't know right from left, especially if they turn the engine around, horizontally!?

Hasn't any of these amateur mechanics ever heard the saying, about which way to turn the nut or bolt: "Lefty/loosey--Righty/tighty?" This goes, except in specialised machinery, or other apps.

Yeah, boys--clamp the "Vise-grips" on it, and smack it with a 10 lb. sledge hammer, or anything suitable! Something will give!

I have seen these things, in my years as a mechanic/auto body man!

I hold the thought that in the future, if the sheet heads don't get us first, that the egg-heads we read about will have us going BBBBLLLL , and hopping around like kangaroos, whilst we try to figure out which way is up!

I like all of the suggestions. One thing to remember it must be really tight.

Adding any type of a wrench puts the torque on one side.

The tool socket idea is my suggestion, but if you use a impact gun it would work.

You will be pitting force at 360 and not on one side.

If that does not work then be like the Beatles "Let it Be!"

Off topic - well what do you know, after not being able to log into this forum for months, suddenly I can, actually I had give up.

Walt Conner

Stick with us, Walt! We value the help you give us! Rustyj

i have the same with my riding mower can't get the plug out affraid i will bust the pop metal on the block will the block take a lot before it cracks help please

Maybe drain what you can from the filter. Angle the machine by putting the opposite side up on blocks. Or use a vacuum pump to evacuate the oil via the dipstick tube.