How often should I change the antifreeze in my car?
A.
It depends on the age of your vehicle, the type of coolant (antifreeze)
in the cooling system and how many miles a year you drive. All late
model vehicles (with a couple of minor exceptions) are factory-filled
with ethylene glycol-based antifreeze. Though the coolant may be dyed
orange, yellow, red, pink, blue or some other color, they contain one
of two basic types of corrosion inhibiting additive formulas: Organic
Acid Technology (OAT) or Hybrid Organic Acid Technology (HOAT).
OAT-based
antifreeze uses chemicals such as carboxylate, sebacate and 2-EHA
(ethylhexanoic acid) to prevent corrosion. Antifreeze manufacturers
won’t reveal the exact makeup of their OAT additive packages because
they are proprietary secrets. But the chemicals are typically
slow-acting so they can neutralize corrosion inside the engine,
radiator and cooling system over a long period of time. Most
manufacturers of OAT-based antifreeze claim their products have a
service life of five years, or 100,000 to 150,000 miles — whichever
comes first (that’s the important part).
HOAT-based antifreezes also
contain an OAT additive package, plus an additional dose of silicates.
These are chemicals that contain silicon and other metals for
protecting aluminum surfaces. Silicates are fast-acting chemicals that
form a protective coating on aluminum surfaces. However, as the coolant
ages, some of the silicates may drop out of solution.
These particles
can have an abrasive effect as they circulate in the cooling system,
accelerating wear on water pump seals and plastic impellers, plastic
radiator end tanks or inside metal heater cores with sharply curved
tubes.
To avoid these kinds of problems, most HOAT-based antifreezes
use stabilizers to keep the silicates in solution, and they contain
only a small amount of silicates. HOAT-based antifreezes that claim to
be “low silicate” formulas should meet the ASTM D6210 standard (which
is a requirement for most late model diesel engines).
Like-OAT-based
antifreezes, HOAT-based antifreezes also have a claimed service life of
five years or 100,000 to 150,000 miles — whichever comes first.
So,
regardless of which type of coolant is in a cooling system, or the
brand of the coolant, it’s important to change any “long life” coolant
after five years of service, regardless of the mileage on the odometer.
Unfortunately,
many people don’t do this and their cooling systems suffer premature
component failures as a result. Five years is not forever. Once the OAT
or HOAT additives in the antifreeze have been used up, electrolytic
corrosion can start attacking the engine, radiator, heater core and
other cooling system components.
Q. What type of antifreeze should I use when I change my coolant?
A.
Use an antifreeze that meets the OEM coolant specification requirements
if your vehicle if it is still under warranty (and that includes
extended powertrain warranties, too). If it is out of warranty, you can
continue to use the same OEM or OEM-equivalent antifreeze, a long life
“universal” antifreeze (compatible with all makes, all models), or even
the older “green” formula standard antifreeze. All are capable of
providing adequate protection for your cooling system.