http://www.caranddriver.com/article.asp?section_id=27&article_id=2334&page_number=1

Patrick Bedard
Top it up with green? Or orange? Which antifreeze?
BY PATRICK BEDARD
June 2002
1 2


It's 2002. Do you know where your corrosion inhibitors are?

Some folks take the yawn approach to what goes on between consenting chemicals in the steamy privacy of a car's cooling system. Not me. And now my sensitivities have been further heightened. It was the weighty check I wrote to a welder for filling in some missing places in a cylinder head that did it. Funny how much aluminum went AWOL in the 30-some years since that engine left the factory, enough to leave gaskets hanging in midair.
Funny? I laughed all the way to Coolant College. David Turcotte is the technical director for Zerex, the line of coolant products from Valvoline. He's a good-natured guy with "Dr." in front of his name. That means he knows everything. So I pestered him until he sent me a package of tech papers about antifreeze and agreed to hold still for follow-up questions.

Modern antifreeze, he says, is 96-percent ethylene glycol, which provides the freeze protection, and four-percent additives. When you dilute that blend 50-50 with water, as the makers intend, you push down the freeze point to minus 34 degrees Fahrenheit. In normal circumstances, you also gain corrosion resistance . . . for a while. The freeze protection is permanent, but the additives are consumed in battle, so to speak.
About half the additive is made of buffers to control acid buildup; the other half is corrosion inhibitors to protect metals.

Perhaps the battle is already going badly in your car. A sticking thermostat can be an early indicator. The next stage: As detritus migrates through the system, it settles in the most confined spaces. If your heater blows cold, uh-oh.
I was hoping that technology, as it marches relentlessly toward obsoleting everything I own, might also have created new antifreeze formulas that would bring forbearance and frustration to the chemicals frolicking under my aging radiator caps.

Of course, no doctor writes the prescription before he considers the patient. The "old" antifreeze technology started in the '60s, improved in the '70s, Turcotte says, and was superseded in cars of the '90s by two new technologies. It turns out that an antifreeze transplant into older cars will work fine with one of the new types; the other will probably kill the patient.
The old technology, a.k.a. "conventional," a.k.a. "inorganic," is green in color. Most of what you see on the shelves at Wal-Mart and AutoZone is conventional, including the yellow bottles of Prestone and the white bottles of Zerex.

One of the new types is "organic acid technology," or OAT. It's orange. General Motors pioneered this chemistry starting with 1996 models in the U.S. and using the name Dex-Cool. Ford changed a few models to OAT, then backed away from it. VW, Audi, and Porsche are OAT users, too, but most others have resisted.
Instead of OAT, most new cars now use a "hybrid" antifreeze that's formulated with both OAT and the silicate inhibitors from green (Japanese hybrids have different inhibitors). It comes in too many colors to pretend this type is color-coded. Interestingly, Turcotte says that as the materials improve for the white plastic overflow bottles of new cars, and they become less yellowing over time, automakers are becoming more venturesome in choosing coolant colors.

The promise of OAT is long-life corrosion protection, on the order of six years/ 100,000 miles for the initial fill instead of the two years/50,000 miles that was typical with the old green stuff. The GM Dex-Cool formula works fine in systems designed for it. But it eats old-style radiators with lead solder, and the inhibitors work too slowly to protect against the sort of corrosion that happens so fast it actually erodes metal—for example, the cavitation likely in the imperfectly designed water pumps of older cars.
"Cars born with green coolant shouldn't be changed to orange," Turcotte advises. It's also a bad idea to mix the two, although the result doesn't immediately turn into witches' brew.

Coolant technology is driven by the makers of new cars to solve new-car problems (same with motor oil.) By the time a car gets old enough to be interesting to a collector, the latest antifreeze blends have moved on to protecting newer alloys and gasket materials. Fortunately, the aftermarket lives by catering to older cars.
As for those aging characters we're keeping around as playmates, no matter what antifreeze we choose, and no matter how often we replace it, Turcotte says the best medicine is to play often. Coolant down in narrow crevices can become isolated, then overwhelmed by corrosion. Once it starts, the best you can hope for is a stalemate. You can't undo corrosion. To keep protection active in all the crannies, the system needs to be heated and circulated every 30 days, he advises. (Hey, Ed., more play days, please.)

Obvious question: What about the water we mix in? He says modern coolants are designed to work with "reasonable" levels of hardness and chlorides in tap water. But magnesium and calcium, the hardness ions, unquestionably contribute to scale and deposits, which hurt cooling efficiency. And chlorides are corrosive. He says distilled water gets rid of all the worries. (It was 58 cents a gallon at my local Wal-Mart yesterday.) Or you can buy "predilute" coolant already mixed and ready to go.
In my vision of purgatory, I'll be sentenced to changing antifreeze in all my cars, day after day, and some archangel with white gloves and a test tube will be checking the color of my flush water for contaminates. I have to keep flushing until he can't tell the drain-out from the distilled he carries in another tube as the control.

Here in this life, I've always changed my coolant. I'm one of those guys who agonize over details. So the job takes a full afternoon for each car. I drain everything that comes out through the cocks, then top up with clear water, warm the engine, and run the heater to circulate fully, then drain again. Repeat at least three times.
What to do with the drainings? I called the local pollution controllers. Antifreeze? Their book had no mention of it. After thinking a bit, however, they told me to put it out back in buckets and let it evaporate. Rocks evaporate at about the same speed.

Old coolant "hanging up" in the system is a real concern, Turcotte says. But he also knows that nobody gets it all out.
"We've done tests," Turcotte says. "If you open a drain cock or drop a bottom hose, you might get 50 to 60 percent out. The best machines, the new ones going into Valvoline quick-oil-change shops, get 80 to 85 percent." This is a manageable level of contamination, as long as the new antifreeze doesn't fight with the old.

Disclaimer:
For documents and descriptions available from this server, the Webmaster does not warrant or assume any liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed.
www.mgfcar.de does not endorse or recommend any commercial products, processes, or services. The views and opinions of authors expressed on this Web sites do not necessarily state or reflect those of the Webmaster, and they may not be used for ising or product endorsement purposes.