I know VW changed coolant formulas in the late 90s, and one of the reasons given was head gasket protection...

DexCool has problems because it eats through the coolant passage gaskets on the intake manifolds.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.