I remember a little while back everyone was questioning whether DEI's Radiator Relief really worked. In the March 2007 edition of Turbo Magazine they put it and 3 other coolant additives to the test. Here are the scans of the pages.

http://i23.photobucket.com/albums/b351/moo...ve/coaddpg1.jpg
http://i23.photobucket.com/albums/b351/moo...ve/coaddpg2.jpg
http://i23.photobucket.com/albums/b351/moo...ve/coaddpg3.jpg
http://i23.photobucket.com/albums/b351/moo...ve/coaddpg4.jpg
http://i23.photobucket.com/albums/b351/moo...ve/coaddpg5.jpg
http://i23.photobucket.com/albums/b351/moo...ve/coaddpg6.jpg

 

great find!!! I am going to use this info once i get my tibby up and running again

 

I have always used Red Line 'Water Wetter' or Royal Purple 'Purple Ice'. Honestly I have never noticed a difference, however I have read a lot of articles that tested them and say they work well. Of course the main factor as to how well they work is directly related to your coolant/anti-freeze to water ratio. Most studies I have read state that the cooling effectiveness of these additives are very minimal at anything over a 30% coolant mixture.
I figure it's cheap ($10-15 per bottle) and you only change your coolant every 2-3 years anyways so why not.