If the coolant is never renewed, how can one be sure that, over a long period, it contains the correct concentration of G13? (For example if it had been topped up from time to time over the years)
I don't really know - but equally as someone who never has old cars or tries to service them myself, is replacing the coolant or checking its anti-corrosion component content actually a thing?
Lots of things I'm aware are maintainance things that occur, but this?
It certainly is in older cars. My 205 handbook advises drain and flush of coolant every 2 years.
Interestingly, the same handbook states that gearbox needs no oil change. The Haynes manual, however, suggest gearbox oil change every 2 years. I did mine a few months back- because it's an old car and I want it to survive forever. If I wanted a car to use for, say, 10 years, I may not bother.
I think the above discussion about VAQ Dif servicing reflects the uncertainty about whether it is worth doing or not. VW don't seem to know what to say to customers.
No reports of VAQ failure. I bet the Dif survives the useful life of the vehicle in the vast majority of cases, without the need for fluid change.
