What's the difference between red & green coolant?

Dear Car Talk

Dear Car Talk | Sep 01, 2002

Dear Tom and Ray:

I drive a Toyota and do all of my own maintenance. I have been using the regular "green" coolant that is frequently on sale, and I change it every couple of years. Recently, I was told by a presumably knowledgeable person that I should only use "red" coolant -- preferably the expensive Toyota brand -- otherwise, I would "freeze" the water pump. Upon further checking, I learned that besides the green and red varieties, there is also orange. Is there any real difference besides the color? Is it just food dye? --Bob

TOM: We knew the color thing had gone too far when we went to Kmart and saw a whole new line of Martha Stewart Coolants.

RAY: There are basically two types of coolants out there, Bob. There's traditional coolant -- the stuff you've been buying on sale, whose additives and rust protectors have a useful life of about 50,000 miles. And then there's the long-life, or "organic," coolant, whose organic additives have a longer life -- 100,000 to 150,000 miles.

TOM: And yes, the colors are just dyes. They're used by the manufacturers to differentiate their products.

RAY: The orange stuff is usually General Motors organic coolant. The fluorescent-green stuff is usually Texaco or Shell, red is Toyota, and the bright-yellow stuff is usually Prestone.

TOM: We say usually, because you can't count on color alone to identify a coolant. There's nothing stopping Fred's Coolant Supply House and Veterinary Clinic from dying its stuff green and selling it. After all, you can't copyright the color green (although I've heard that Bill Gates has tried).

RAY: So the important piece of information is whether the coolant in question is a traditional or long-life coolant, Bob. In your case, I'd guess the stuff you're getting on sale is traditional coolant. And for you, that's fine, because you change it every couple of years.

TOM: If your car comes with a long-life coolant, you should try to add only long-life coolant when the reservoir is low. There's no danger in mixing traditional coolant and long-life coolant, except that once you go beyond 15 percent traditional in your mix, you'll get the shorter life of the traditional stuff. And since the long-life stuff costs a lot more, that's kind of wasteful.

RAY: And by the way, as long as you're using the correct type, you don't have to buy the expensive Toyota stuff, Bob -- unless, of course, it matches one of the color schemes you've got going under your hood there.

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