Best Penetrant to Remove Differential U-Bolts?

I was wondering about what to buy as well.
WD40 used to be the standard for me but screw those guys...I've had almost every can in the last couple of years develop some failure.
Some would only spray sideways, upside down or after shaking. Some just quit spraying even with the can about 1/2 full.
PB Blaster smells bad to me but it does seem to work.
Never tried Kroil but I have heard that it is NOT cheap.