Anything phosphate-free will do the job. Spending more won't get you more. I
bought Pentosin for my Saabs but ain't gonna no mo.

How do you get all the old coolant out? I don't think it's possible. Not if
you really mean "all." Most, ok.

And what do you do with the old? It's so toxic you can't just dump it into
the street, yet there's so much of it you can't just stick it in gallon milk
jugs and recyle it.

Pretty good discussion of coolant types at http://www.westfalia.org , under
"Tips."