There is nothing special about the coolant approved by Porsche. It must be ok for aluminum, as the block and heads on all current Porsche models are made of aluminum. But this was also true for the 924 - 968 series, and the 928. The older cars used GM Dex-Cool approved coolant as it does not have phosphates which eat aluminum. Same is true for the Boxster. Porsche does not make coolant.
I contacted Chevron/Texaco in the US, which owns 50% of the euro company that makes the coolant sold by Porsche under the Elf/Arteco brand. Chevorn/Texaco then contacted their euro partner.
The link is to my post. Meets the performance requirements of Porsche but "not yet approved." If Chevron/Texaco paid money to Porsche I bet their US sold coolant would be approved - but that will never happen as Chevron/Texaco owns 50% of the company that makes the Porsche coolant and they would be competing against themselves. If the chemicals in the coolant are the same - then it is the same.
Porsche approves several different brands of oil - but my rear trunk lid has a Mobil 1 sticker on it. I'm sure Mobil paid Porsche for that sticker.
That is my rant. Jeff
http://www.babblers.org/board/archive.pl?read=22497