AussieSavage wrote on 12/31/69 at 16:00:02:In Australia we have a spray called RP7, it loosens rusty frozen and sticky parts and it works a treat. Just apply the spray and then wait 2mins before putting a wrench on the oil drain plug.
In the US the best penetrating oil I've found is PB Blaster. You can find it at most auto parts stores.
The best wrench you can use is a 6 point socket on a breaker bar. It's much easier to strip the bolt head with 12 point.