You shouldn't lose any coolant when replacing the oil cooler O-ring. The
'easy way' is to remove the filter, then the nut and threaded tube, which
will allow the cooler to swing away from the block far enough for o-ring
replacement. No reason to open the cooling system this way.

Karl

-----Original Message-----
Hello listees,

Does anyone know if you can mix the blue VW coolant and the orange Prestone?
  I didn't get a chance to get some of the blue that last time I was near a
dealership (I live out to sea) but I think I can get the orange from the
NAPA place on island.  I want to replace my oil cooler O-Ring and so I won't
be losing all my coolant.  Right now I've got the blue in my van.

Thanks in advance!
Marla
'87 Westy GL Van "Morrison"