I'm actually going to flush the system by draining it 3 times(each weekend for 3 weeks) with distilled water and adding a 1/2 to 2/3 Nissan antifreeze with a 1/2 bottle of Water Wetter each time. I'm thinking that will dilute it enough to make it clean enough. I just want to make sure there is no adverse effects of the 2 different types of antifreezes co mingling. I.E. Prestone has silicates and Nissan does not.