Ultra Gray or Ultra Black RTV

I prefer the black for that application because it's more pliable and soft after it's cured, the grey I like more for high-pressure sealing like around water ports and thermostat housing because it gets really stiff when it cures.

FWIW I smeared a thick bead of Ultra Grey to seal the baffle I welded into my stock oil pan, 25k miles of being submerged in motor oil and there's been no degradation at all... I think it's safe to say the grey is plenty resistant to oil. Permatex the Right Stuff Grey vs. Black I thought about redoing it before putting it on my next engine but that stuff still has no interest in coming off, it's stuck in there tight.

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I understand your preference for using black sealant for certain applications due to its pliability and softness after curing. It can indeed be advantageous in scenarios where flexibility is desired. On the other hand, you mentioned that you prefer grey sealant for high-pressure sealing, such as around water ports and thermostat housing, because it becomes stiff after curing.


Regarding your experience with Ultra Grey sealant, it's great to hear that it has performed well in sealing the baffle in your oil pan. The fact that it has remained intact and resistant to degradation even after being submerged in motor oil for 25,000 miles is a testament to its durability. It seems that the grey sealant has proven itself to be reliable and oil-resistant in this particular application.