That's a lot different than your previous statement that regular
antifreeze would corrode heads to the point of failure.  I'd also have
to take issue with MB water pumps lasting 30 years.  I see folks in the
newsgroup frequently here with pump failures long before that, many
under 100K miles.

I did quite a bit of looking on the web and found opinions all over
the map on this, not just about MB, but BMW, Volvo, etc.   Just about
all of it seems to come down to the manufacturer recommends it and then
people have all sorts of explanations as to why.   Among the claims I
found:

"Just look at the insides of a cooling system that uses regular
antifreeze and you'll see white deposits that shows the stuff is bad"

But isn't this actually phosphate or similar deposits that are in the
antifreeze for precisely that purpose, which is to say to allow a
coating which protects the metal?

"The higher PH of regular antifreeze causes the plastic components of
the system to fail"

That seems very strange, as everything from drain cleaner to acid comes
in plastic bottles.

"The non-MB antifreeze causes pre-mature corrosion, due to the
mechanism you cited above"

But, as I've said, there are plenty of antifreezes around that the
manufacturers say can be used in any car, and certainly many of today's
cars have aluminum as well as plastic components.  I've seen no damage
to the aluminum componets in my 26 year old car.  By now you would
think there would be an uproar if cooling systems were failing because
of these products.

The only authoritative explanation of what is going on that I could
find from a manufacturer was from Peak, which I included below.  Of
course they have a vested interest in std antifreeze, but at least they
have an explanation, which is that the European manufacturers don't
recommend antifreeze with phosphate because if used with hard water,
which is typical in Europe, it can lead to precipitation and blockage.

It would seem to me that the easiest and safest thing to do is use the
Zerex G5 as it clearly meets MB requirements and only costs a little
more than regular antifreeze.

http://www.peakantifreeze.com/tech/tech_b.html

In many US and Japanese antifreeze formulas, including those produced
by Old World Industries, phosphate is added as a corrosion inhibitor.
European vehicle manufacturers, however, recommend against the use of
phosphate containing antifreeze. The following will examine the
different positions on this issue to help judge the pros and cons on
phosphate inhibitors.

In the US market, a phosphate inhibitor is included in many formulas to
provide several important functions which help reduce automotive
cooling system damage. The benefits provided by the phosphate include:

Protect aluminum engine components by reducing cavitation corrosion
during high speed driving.
Provide for corrosion protection to ferrous metals.
Act as a buffer to keep the antifreeze mixture alkaline. This prevents
acid build-up that will damage or destroy metal engine parts.

European automobile/ truck producers feel that these benefits are
achievable with inhibitors other than phosphate. Their main concern
with phosphate containing products are the potential for solids
drop-out when mixed with hard water. Solids can collect on cooling
system walls forming what is known as scale. This concern comes from
the fact that European water is much harder than water in the US.
Because phosphate "softens" water by forming solids of calcium or
magnesium salts that can drop-out of solution, there is potential for
cooling system blockage. The phosphate level in most US and Japanese
antifreeze formulas do not generate significant solids. Furthermore
modern antifreeze formulations are designed to minimize the formation
of scale. The small amount of solids formed present no problem for
cooling systems or to water pump seals.

For now, Old World Industries believes that phosphate will remain a
primary ingredient for cooling system protection. Still, as a good
corporate citizen, we continue research on other inhibitor types that
will provide the same benefits without phosphates. To show this
commitment, Old World Industries is now marketing a heavy-duty
antifreeze that incorporates a phosphate free inhibitor package. This
new product is called Fleet Chargeâ antifreeze. It is a universal
formula that passes both heavy-duty and automotive specifications.

In most US and Japanese vehicles, you can use either a phosphate free
or phosphate containing antifreeze during the warranty period. However,
phosphate containing antifreeze can void European OEM warranties. Old
World Industries advises that only recommended antifreeze types be used
in these vehicles during the warranty period to ensure complete
coverage.