I prefer BG's Enforce penetrant. It's commercial grade stuff so you'll have to buy it from a shop that uses it. If paint damage isn't an issue, I heat the area around the fastener to expand it then put some torque to it to remove it. If you heat the bolt, technically you are expanding it even tighter.
Scott

Scott Ward

2 1948 1.5-ton Loadmasters
The red one and The snow pusher
1 1950 3100
1 1955.1 Chevy 6500
1 1954 Chevy 6500 2-Ton
1 1955 1st Series COE 5700
1 1963 K20 (454)
1 1964 C10 (350)
1 1951 1.5-ton Dump Truck
1953 and a 1956 Ford F800

Raising a teenager is like trying to nail Jello to a tree!