I know you tried penetrating oil, have you tried a product like Jigaloo?
It has worked twice for me on very stubborn hinges. The first one was the door hinge on my Sierra, I had to spray it several times a day for a few days before it finally started working again. I swear that I opened and closed that door 300 times in a few days... just to work the product into the hinge.
I also had the side door on my utility trailer completely seize the hinges. When I attempted to open the door, the wall of the trailer was actually bending where the hinge attached, rather then the hinge opening up. I went out to the trailer each night after returning home from work and sprayed the hinges. I kept trying to carefully open the door. Eventually the door started to open a little bit on the hinge. I kept at it for awhile and now it works just like new again.
I spray a fluid film on the exposed hinges now to prevent the problem from occurring again. Those hinges are also the rod type with no water escape route.