Hmmm so reading and researching I know Ultra Black is recommend over the grey but also found they make a "gear oil" rtv, yes made by the same company as the ultra black. Curious if anyone had used it?
I have not, but have used the ATF RTV that is designed for trans fluid, which is more detergent based than motor oil.
I ironically have found, through experience that using different types of RTV can be better in most cases, where Ultra Black is used on the engine oil system, copper RTV on exhaust and the EGR system, and specialized RTV for trans and other stuff.