To use sealant or not?

Changing the thermostat housing on the M50 motor in my BMW. Do you guys use a little RTV around a coolant fitting when there are orings built into the part? Or just use the orings the way the manufacturer designed them?

Thanks, Bruce

If the seal is an o-ring, no.

If the seal is a gasket, yes.

I've never used sealant with o-ring seals. For that matter, I don't use sealant with gasket surfaces when the gasket pulled off easily (rare). Usually the gasket surface needs sealant because of the dumb ox (me) scraping the gasket surface clean, while o-rings almost always come off without any hassle. I have used a tiny bit of gaskacinch or similar to hold the o-ring in place on tricky ones, but that's not intended to help the sealing, just to make sure the o-ring doesn't move and get pinched.

Bryce