Dropping the whole thing in diesel
will often work, its a bit cheaper than half a can of your choice of super spray. Patience and a gentle warming. If after this it still wont budge (see NoTies post) then give it a wack with a hammer....No I am not joking....Dont do it so hard that you bend the little shaft. The idea is to "crack" the layer of corrosion
to allow the oil to penetrate. Throw it back in and wait a bit more. The game
is to use just a little bit less force and teeth grinding than what will break both !!