I was playin' around with a refractometer today, and realized I had not checked coolant concentration in any of my own cars in a long long time.
On my wife's '02 Jetta it was 55%, on my company car it was 58%, and on the '98 A4 *36%*! hmm, my only guess is that during a dealer /shop visit, a tech noticed the coolant a bit low and topped off w/ water only. I would think this was a cumulative effect of happening more than once; each time the tech thought "it's only a tiny bit low, just adding water and no coolant won't throw off the concentration". but do it 2,3,4 times and there you go.

NEway, it looks like I'm gonna need some more G12 to bump the conc. back up. I'm gonna shoot for 42%-44%.