I've only had the car 8 months and the PO replaced the radiator recently.

As an educated guess I suspect that whatever additives the companies use that they are both buffered and over-designed.

I suspect that even at 10% AF the system would have an adequate amount of beneficial additives.

Recently there was a thread where someone mentioned testing for the acceptable presence of some AF additive by measuring the resistance to ground by sticking your meters probe into the water/AF mixture and having the other probe connected to the block.

He said it was in the FSM.

Please realize that I am giving you my best estimate and recollection and that I know something about some of the chemistry of these systems but not the specifics of AF design.

Anybody who claims to know more (besides some basic concept that I'm sure about) almost certainly does.

It is nice to be done and have good confidence that the car is in good shape.

Later.