I change the coolant (Dexcool) in our vehicles, a 1999 4.8L Silverado & a 1997 3.1L Lumina every 2 years (rad only, not a complete flush). Never had any coolant related problems, fluid is always "crystal clear orange". I feel comfortable doing it this way, the system is getting "fresh" 5-year coolant every 2 years. Our vehicles do not get driven very much, maybe 7000-8000 km/year, 65% city, 35% highway. My wife can walk to work, I cycle in the warmer weather. Cheap maintenance. I can about get half the coolant capacity out of the Lumina (overflow tank included) and about 70% out of the Silverado. Here are my questions (finally!!): Should I be adding the GM sealer pellets when I do these rad drains and is my method OK?