Best Penetrant to Remove Differential U-Bolts?

In that video above, he is using Fluid Film in the wrong application, that's why it does not work well. It's not made for use as a penetrating oil, even though it says that as one of the uses on the label. It's best use is for coating parts for storage so they will not rust. For that, it is badass. I like that guy's tests, too. Look how well the Sea Foam does. I've been tellin yall that stuff is the shizzle.
Fluid film if you arent in a hurry.
But a little heat improves capillary action greatly. I always keep a can around.