I also use Kroil, but it isn't readily available to most people, and that is why I recommended the SeaFoam Deep Creep. I buy the Kroil from Amazon, and I like the liquid in the can vs. the spray. Both are about the same money, but there is more in the dropper can than in the spray can. With the dropper, I can put it exactly where I need it. I also have penetrants in small medicine dropper bottles for the more delicate work.
I just received a new penetrating oil from CRC that I was asked to evaluate. Still haven't had anything to try it on. I will have to look around the backyard for some rusty metal to see what is so badly rusted that it won't come apart. That should be a good test.
I use Kroil in the spray can only occasionally.
Several years ago I bought a gallon of Kroil (expensive), and I have shared it with one of my sons.
I just use that in an old oil can.
I had a top link that was seriously rusted together (left outside for years).
I tried the smoke wrench, and everything else I could think of, to free it up.
Finally stood it up in a corner and added several long squirts of Kroil to the inside threads.
Left it standing that way for 5 months.
Bingo!
Pipe wrench freed it up easily!