Love CarTalk for years! Funny story 2013 I purchased Hyundai Accent. Now have about low 25,000 miles. I usually check the coolant thru the overflow and add a little water. So three months ago I took the radiator cap off and the coolant looked clear. I am used to green or brown but not clear. I said, “Oh, my God, the coolant is bad.” So right away I got the mechanic to change my coolant. Twice I mentioned to two other mechanics that my coolant was clear and they never once said it is a new type of coolant. So now I learn there is a coolant that looks clear! Wow times change.