I have been using the Napa Auto Parts Super Penetrating Oil. I will spray the bolt in which manner which I figure seep down onto the threads. Wait a little bit. Sometimes I will go out day in advance and spray things down. I will spray the bolt again just before attempting to remove a bolt or nut. When I start to remove the bolt and it feels like its starting to bind I will turn it back the other way and will often work it back and forth with a wrench or socket. I am successful 80%-90% of the time with this method.
Also popping the head of the bolt with a hammer sometimes helps loosen the corrosion.
It is always better to get the bolt in one piece as drilling out bolt is a pain and sometimes impossible depending where the bolt is located.
Hope this helps.
Walt Williams
La Verkin, UT
