Bullseye!

[HawkinsHollow]

Not in one day, it will lube it enough to pull off. Besides wood is contained inside an axe head and the swelling creates pressure to hold it.

I beg to differ. The oil will instantly soak into that log as dry as it is. The fence post is contained inside the wood, no difference. The only way to see who is right is to test your theory. Probably not going to happen. So I guess the world will never know.

 

[CoyPatton]

Wedge and maul to try and split it around the post. Probably be slow going since the post will shake

Definitely a direct hit..

Support either the round or the T-post to reduce vibration.
Many ways to do so, but 1st order going from photo will be to clean wood out of way of your approach. Support T-post with a piece 2x with a V notch in one end and a stake driven as deep as possible on the other end of the end of 2x.
If supporting round, I would use loader bucket and cut a round to make it a fairly tight pressure, without pushing on T-post.
Either approach should minimize the vibration and thus the bending of the T-post.
T-post are usually fairly easily straightened using receiver hitch on truck or cross tube on loader.

 

[charlessenf]

"What are the odds?"

Hmmm, going to need a bit more data to calculate that. Height of the oak tree, age of the tree, when sign of infestation/rot was first noted, caliper at 36" above ground level, lean of the oak in relation to the fence line in question, distance between impaling post and base of oak tree, average rainfall experienced, wind speed averages, and a few others that will come to me as we mull your question over the next few months or so.

 

[gtunney]

I beg to differ. The oil will instantly soak into that log as dry as it is. The fence post is contained inside the wood, no difference. The only way to see who is right is to test your theory. Probably not going to happen. So I guess the world will never know.

Well, if it is still stuck after the oil application, it should certainly burn...