Hi,
I would strongly discourage this from being done if you have a newer vehicle with the extended life coolant. a) Antifreeze does not last forever. My guess is that you live in a warmer climate where you don't need the lower freeze point (when I lived in Miami I could use straight water and didn't have any problems). 2) Extended life coolant has a very different chemical make up as regular antifreeze. I don't know this part for a fact for Audi/VW extended life, but with GM, Ford and Chrylser, if you mix regular with extended you end up with this pretty little gel. You can do a complete flush of the original antifreeze to regular, just make sure it is a complete flush. Don't just drain the radiator and refil it. Also to the original poster, check your owner's manual. "Lifetime" is a subjective term, if it lasted til it died, it lasted its lifetime. I'm basing this statement on US extended life coolant, but you should probably have your coolant system flushed at 150,000 miles (I'm not sure what country you're in, Denmark maybe? regardless, you probably use metric since I'm pretty sure the US is the only place that doesn't use it, and I have no idea how many km that is) or 5 years.
HTH Enjoy Bill
91 Audi 200TQ with green coolant that was flushed last year
96 Chevy K1500 with extended life coolant that was flushed at 5 years
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