I've been using red for a while and every time I go get some the price is a little higher on the stuff. Last time it was about $18 a gallon. I think it's more important to not mix the green and red than either using one or the other. Just keep up on changing it on time and you should be alright. The difference is that there are no silicates in the red. I like it better but it will find leaks easier than a coolent with them.
