-- It was in My Valiant, when I bought It. Apparently it was there to mask a external head gasket leak. - Because the car ran hot, I guess for several reasons, I pulled it out. After that the leak became major, BUT the temp went down. -- I've since heard from several guys that it (Evans) causes higher operating temps, in spite of their ads. -- See info at -- www.norosion.com/evanstest.htm --- For me. I do not want to get fooled into ruining My motor, because the coolant didn't boil until 375 degrees. -- Hot Is Hot regardless of boiling point.