I thought the coolant change interval was listed in the owners manual packet,, but I sure can't find it now. Is that change interval shown somewhere? I have found that the coolant needed is Spec. 325.0 which is Mercedes part #BQ 1 03 0004, but darned if I can find the interval for my Smart. This coolant is a 15 year/150,000 mile coolant for many Mercedes models.