that was the only coolant they say it has to have, or using the green ethlyne glycol would pose a corrosion threat to certain metal in my engine. That what they said at least. Anyways as far as those coolants going 100,000 miles i'm not too sure about that, as i would rather not take the chance of break down after warranty expires (36K) I had changed mine every year or 12-15K miles anyways, even if it said 5/yr 100K. Just my two cents, and niXit is correct on his earlier post.