Well, I am one of those stupid folks. I even buy 50/50 for my commercial heavy diesels. I don't have the time or inclination to play around with mixing stuff. And it isn't like one is changing out the coolant every year anyway. A few gallons of 50/50 for the typical car or pickup? Most people waste more than that on a Saturday night. Even replacing larger amounts in my semi trucks, using 50/50 is cost effective. And even though not every single drop of coolant is removed when changing, what is in there is 50/50 already, so the mix after filling back up will be 50/50 again. Nice thing is, the coolant I use, I can use it for all my vehicles. From my personal on up to my commercial vehicles. I get the Final Charge ELC from my supplier and use it across the board. It's an OAT coolant.