The penetrating oil will wick in to the threads more if applied when the object is warm. It will wick in as the object cools. Care and prep in the event of a fire while doing this should be taken. Strike the threaded portion several times from side to side, then apply significant torque to the fastener ending with the final amount of break-it-free torque in a snapping/sudden movement. Slow and steady torque vs. snapping it loose in my experience causes rounding of the hex sides.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer