Is it critical to change coolant at 100K?

[RMcG]

Thanks tmontague and johnwk and others,

I just checked the coolant by dipping my fingers in it and rubbing them together and it definitely feels slippery and oily.

Does anybody else have any suggestions as to the best way to dispose of the old coolant? I want to do this in an environmentally sound way.

Does anybody else have any feelings about using distilled water as a rinse as johnwk suggests?

Thanks,

R.