Kroil and PB Blaster are the same type of thing, but I don't think the Kroil smells as nasty as PBB.

One other product to try- FreezeOff, made by CRC I think. I've used it on the old 36mm collar nuts on my Porsche's oil lines which are famous for practically welding themselves with corrosion to the oil line threads. Very easy to damage or strip the threads if not careful. You spray FreezeOff on the part, causing it to shrink a tiny bit. Then when the part comes back to room temp, it's easier to remove presumably because the shrink and expand process helps break the corrosion holding it all together. Sort of heating it but in reverse.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R