As with any coolant, you must replace it every 2 years. The reason is any
water contact with metal... will create acid... so over a long time... it
will start to eat your gaskets... metals.. etc. This is why you see coolant
Mechanic don't tell you this or even think about it because they want
business for repairing big stuff that cost you $$$.
As for MB coolant being superior... that's because I read reports on
composition and how they are formulated. The green stuff has qiute alot of
silica... it is a necessary component of coolant protection... However, the
coolant is set to be alkaline... alkaline is not good for engine either...
but okay... Anyway, so as the coolant gets old... it goes from alkaline
toward neutral to acidic.
MB coolant is much less silica... which is better for aluminum engine... and
the coolant is buffered base... meaning it is formulated at near neutral pH
level... the pH remains at that level until it is exhausted and then it goes
toward acidic pH.
So technically, MB coolant is superior because it protects the engine by
having the pH remains near neutral for far longer time before it is
Whereas the green stuff is caustic either way and does not stay at near
neutral for long because it is like your fuel gauge... goes from alkaline to
acidic as you empty your gas tank.