I recently purchased a new 2006 Elantra GLS, and have a question
regarding engine coolant and anti-freeze. I've been a firm believer in
using the low-silicate, low-pH, phosphate-free ethylene glycol
coolants, such as the Mercedes-Benz OEM coolant, in all of my cars. I
have observed engine tear downs of engines using the old green-colored
Inorganic Acid Technology (IAT) coolants vs. the Hybrid Organic Acid
Technology (HOAT) coolants, such as the M-B coolant, and the difference
was very apparent. The old green coolant etches and evenutally "eats
away" aluminum parts in an engine and cooling system.

There are three basic technologies in ethylene glycol coolant: 1). The
old green-colored type that we're all familiar with using the Inorganic
Acid Technology (IAT), 2). The HOAT-technology based coolant such as
the Mercedes-Benz coolant which is actually manufactured for M-B by
Valvoline. This is Zerex G-05 coolant by Valvoline, and 3). the
Organic Acid Technology (OAT) coolant, such as DexCool by GM, and
available from other sources as well, including Peak, Prestone, and
Valvoline.

OAT coolants are not only phosphate-free, but also silicate-free, and
low pH.

Now (and, Hyundaitech if your reading, please add your thoughts to this
discussion), here's my question . . .

Since Hyundai does not sell its own branded coolant like Honda, M-B,
etc. do, what is the factory specification of the coolant supplied in
current Hyundai vehicles? The Owner's Manual for my 2006 Elantra
simply states to use an ethylene glycol-based coolant - period.
Nothing about the actual formulation. I do know the original coolant
supplied was green in color, thus it must be the old-standard IAT
technology-based coolant. I checked with my local Hyundai dealer, and
the Service Manager said: "We go over to NAPA and buy their standard
coolant for all applications." Interestingly, he had never heard of
the 3 types of coolant technologies available. Nor, does he use
de-mineralized water or distilled water, as I have always done since
the late '60s.

According to many of the coolant manufacturers' websites, they imply
that the OAT coolant, specified by Honda, is best for all Asian cars.
GM's DexCool is OAT-based, as mentioned previously, and the only
difference between it and any other OAT-based coolant, such as Honda's,
is the color. However, OAT-based coolant is NOT compatible with
IAT-based or HOAT-based coolant, so you have to do a complete and
thorough flush, which is almost impossible in the real world by the
D-I-Y'er (Do-It-Yourself). On the other hand, IAT-based coolant and
HOAT-based coolant are compatible.

As I previously stated, I've used the HOAT-based coolants for a number
of years, and have never experienced a coolant-related failure, and
from recently replacing a water pump in my SAAB, the aluminum casting
looked brand new without any etching of the aluminum. But, should I
consider the OAT-based coolant for the 2006 Elantra, or just stick with
what I've used in the past? OR, am I being too technical and
obsessive, and just use the approach of the Hyundai Service Manager and
just use "any old coolant?" BTW . . . I typically change coolant
every 2 years, which is also the Hyundai recommend maintenance spec
interval on the Elantra.

Thanks for listening!

Don