Over the years I’ve tinkered with a bunch of different cars. Back in the day, you could put green ethylene glycol coolant in every car and it worked fine. If you had a car with the brand new DexCool, it was recommended to drain it and refill with the green stuff. Then some manufacturers went to the red stuff, and VW/Audi went to some other stuff that sludges up if mixed with the green stuff. A couple years ago I bought an insurance auction VW Beetle TDI, and when I replaced the front end/radiator/etc., I flushed the engine out with water and switched the car to traditional green coolant. My ’06 Mustang has 140K on it, and living in a constant state of having too many projects, I’ve neglected to change it until now. I’m of a mind to flush it out and run green coolant, but I know aluminum motors aren’t exactly tolerant of the green stuff. I intend to transition my entire fleet to one coolant. What is a good one-size-fits-all coolant that is readily available? I’m in Oklahoma, and it freezes here, so running straight water is not an answer. Should I stick with the green stuff and replace it more religiously? The Mustang is bone stock and ultra-reliable, so I don’t wa...