[Vwdiesel] block heater seal question

[Gary Shea]

I got a replacement block heater for the dead one in my Rabbit.  The old
one was installed with liberal amounts of some RTV-like sealer... the
new one says "don't use sealers with this block heater as it will rot
the o-ring".  I'm not sure I trust the o-ring to seal... the surfaces
involved are not exactly machined to a high gloss!  And I sure prefer to
deal with it now rather than when the head is back on...

What do y'all use to seal the block heater?

        Gary