Put a blow torch to your oil pan!?!?!? That's a bit of a radical solution, isn't it?
Put that adjustable wrench away before it does any harm! They suck for most applications, in my book. I prefer to use a box-end hand wrench for sticky nuts and bolts...
I think that's the most secure and reliable wrench for high-torque applications. I've split sockets on stuck bolts before, and broken adjustable wrenches, too. Even a cheapo box wrench will not open up or turn out the corners on a bolt.
Good luck!