You've got the hood up for the first underhood check in a while, which isn't surprising in this era of self-service gas. Checking the coolant level, you see that it's down. You don't carry a jug of antifreeze with you, so instead of do ing anything, you just worry about it until you get home. Actually, you realize that it's finally time to change the whole system, not just top up.
At least the auto parts store is on the way home, all the better to pick up a couple of jugs of antifreeze. But what kind? The parts store now stocks three colors: yellow, green and orange. Huh? Isn't all antifreeze green? Isn't it all the same?
Bad News, Good News
The bad news is that it doesn't come down to color matching. Isn't all antifreeze compatible? Sorry, but it isn't. There are a few cases where you can get a fast case of corrosion, some where the water pump can be both eroded and corroded to an early death, and a lot of cases where you can shorten the effective life of the antifreeze. Antifreeze itself (most commonly a chemical called ethylene glycol) doesn't wear out–ever–but the key ingredients are the rust and corrosion inhibitors, and they get used up. The most common inh ibitors, silicates for aluminum protection, are used up faster than others. That's why some new cars (all General Motors, Mercury Cougar, VW/Audi models) have red or orange antifreeze with a new class of inhibitors, called organic acids. Examples of U.S. brands with these organic acids: Havoline Dex-Cool and Prestone Extended Life, both recommended for five years or 150,000 miles. That's the good news.
Fill 'Er Up
How about just pouring orange antifre eze into every cooling system, say, yours? Sorry, but it's not that simple. The new organic acid antifreezes may be used only if the cooling system has an aluminum radiator (rather than copper-and-brass).
However, let's assume the reaso n you're thinking of a coolant change is because you're changing a cooling system part (pump, radiator, heater, thermostat housing) on a system with a conventional coolant, not an organic acid orange or pink. In that case, don't change to organic acid ora nge, even if the part you're installing is aluminum. Use a fresh fill of familiar U.S. yellow/gold or green silicated antifreeze.
The two orange extended-life antifreezes are compatible with each other, with what's factory-fill in GM ca rs and the '99 Mercury Cougar, and with the pink in VW/Audi cars. However, they're not compatible with a special orange antifreeze in 1998-99 Chrysler L/H cars (Dodge Intrepid/Chrysler Concorde and 300M), a special "hybrid" mix of organic acids and silicates. The green in most Japanese cars contains no silicates, so it's not the same as the green in the parts store. The yellow in some European cars contains some silicates, but it's very different from yellow Prestone, the top-selling U.S. brand. And then there is red antifreeze used by Toyota, and blue used on some European and Korean cars.
Freshen Up That Cup For You, Sir?
What about just topping up a system that's low? What kind should you use? If the system (except for Chrysler L/H) has orange or pink, use Prestone or Havoline orange for top-up. All you have on hand is regular U.S. yellow/gold or green? Well, if you're desperate, use what you've got, because it's better than running low o n coolant and possibly overheating. But the mixture is shortening the life of the antifreeze. By how much? It would take lab tests to tell, so the best deal is to do the equivalent of a "retrofit." Can you retrofit all systems? Sorry, the answer is no. What about draining green or yellow/gold from the radiator and refilling with orange? Is that considered a "retrofit"? No, and you'd better not try that, either.
What if the system has Japanese green, Toyota red, Korea n or European blue, or European yellow? As we noted, European and Korean formulas have silicates, so U.S. gree
