A new day, a new question: I have an E 320 CDI T-model, Bj 5/2000, 140,000 km, there is in the service booklet under “additional work every 3 years: coolant change”. My free workshop means: “Do you really want to do this to yourself?” Does this really make sense or is it covered? Can only affect the corrosion protection in the cooling water, frost protection and cooling effect do not age, doesn’t it? Does the change also help to prevent the calcification of the cooler? 5 years with approx. 100,000 km it should still last … Thanx