Porsche claims their coolant is Lifetime, but don't believe it. It is
simply a silicate and phosphate free Glycol based coolant. This should be
changed every 5 years/150k mi. (whichever comes 1st) in order to
provide maximum corrosion protection. It is the organic carboxylates
which breakdown after this interval.
Instead of buying the super-expensive Porsche Coolant from the dealer, Zerex Extreme
Life 5/150, Texaco Extended Life, Shell Rotella® ELC Extended Life
Coolant, UNI-GARD 5/150, Mercury Extended Life Coolant Anti-Freeze, all meet or exceed
Porsche Coolant requirements and are much cheaper. Use of any other
type coolant is not compatible with the system and can form a gel-like
substance if mixed with the proper coolant which can then obstruct
flow, create hotspots, etc.