About 7 years ago I flushed out the green coolant in my 1991 Chevy
K1500 pickup with a 4.3 V6. The truck now has about 97,000 miles on
it. Normally, I would say stick with whatever coolant came from the
factory but the orange coolant seemed like a better choice at the
time. I liked the fact that it had a 5 year or 100,000 mile life, and
the container said that it was easier on water pumps. It was also
ethelyne glycole based and seemed to be very similar to the green
coolant so I figured why not try it. After flushing the green coolant
out, I replaced it with the orange coolant (I think it was texaco) and
mixed with distilled water.
My water pump recently started leaking, I don't think it was the
orange coolant, just age. I have not had any other problems with the
cooling system, but I have recently heard some bad stories about the
orange coolant causing head gasket damage, intake gasket damage, and
water pump damage, on some vehicles. I've also heard stories about the
orange coolant "sludging up" but I have not noticed that problem yet.
On the back of dexcool containers, it says the coolant is for use with
1994 or newer vehicles and that on some vehicles (mine was not listed)
if you did not change the coolant at least every 2 years, cooling
system damage could result.
I'm going to flush the system & replace the water pump, upper and
lower radiator hoses, thermostat, and radiator cap. Should I keep
using the orange coolant or go back to the green coolant ? I would
stay with the orange if I new it would not hurt anything, otherwise in
the absence of an answer, I am inclined to go back to the green stuff,
providing it won't do more harm than good.
I'm not sure why GM specifies 1994 or newer vehicles and I tend to
wonder what the difference would be between a 1994 4.3 V6 & a 1991 4.3
V6 ? Are the seals or metals used different ? That's about the only
think I could think of that would make a difference.
Is there anyone out there from a GM service department that knows the
answer ? I'm hoping a mechanic or GM tech may be able to answer this
question with a reasonable degree of certainty.
Thanks for your help.
Although we have several people here who are professionals and who
work for dealerships, finding the "answer" is a little more difficult.
I am a chemist and have worked in research and service for years, until
my retirement in December 2006.
I have personally tested products like Dexcool under laboratory
conditions and, of course, have followed the products to field applications
The original "green" formulations were pretty good for most applications.
They were all based on ethylene glycol in the early days, and the corrosion
inhibitor packages contained materials to protect iron or steel, solder,
and aluminum. (These are the same basic metals that are still used in
cooling system construction).
The biggest problems with the older green formulas were -
(1) silicates, used to protect aluminum and its alloys, could precipitate
conditions and form glassy deposits in the radiator and other parts of the
(2) some of the components of the package were not deemed environmentally
by authorities in some countries.
The silicate problem was not always seen, and could be avoided by using
products, decent water for dilution and reasonable maintenance.
Later, propylene glycol began to be used instead of ethylene glycol because
it is a
good bit less toxic than ethylene glycol. It is somewhat more expensive
and is somewhat less effective as an antifreeze, but overall not a bad
The Dexcool type formulations were based on Organic Acid Technology, or OAT.
Early patents by the Japanese were the first examples of this that I have
They were environmentally better than "green", but had some limitations.
they had no long term inhibitor especially for aluminum (and we all know
is used more and more in modern vehicles to save weight and cost).
HOAT was developed to try to improve performance versus aluminum. HOAT
some silicate components, at decreased concentrations usually, to give both
AND to try to minimize the accumulation of silica deposits in the engine.
You pay your money and take your pick. AFAIK, there is no basic difference
in the metallic
materials used in engines now versus 10-15 years ago. We may be getting
more aluminum now
and less brass, but the basic compositions are similar.
If your warranty depends upon the coolant you use, then keep your warranty.
No matter what you use, it is wise, IMO, to flush out the cooling system
every 2-3 years and
replace with new fresh coolant. Corrosion inhibitor packages do not last
forever. They degrade
due to shear, hydrolysis, oxidation, and adsorption onto particulates. Even
the glycols can
oxidize with time, if you have any contact of the fluid with air. And,
although that contact
is minimized with the expansion tank systems now used, it will eventually
take its toll. When
you oxidize ethylene glycol, you get a mix of compounds related to glycolic
acid and oxalic acids.
I probably have used more bandwidth than necessary, and I am sure some will
points of view, but these are the facts as far as I have personally tested
I am no great fan of Dexcool, but it does NOT destroy head gaskets. That
was a myth.
Sludging was due to the type of rad cap.
More info here,
I have an interesting question and I would like your opinion since you are a
I just picked up at the beginning of February a 2003 X-Type Jaguar from a
littlie old lady ( for real she is a relative) that had 3200 miles on it. It
now has 4700 miles. I changed the oil immediately but decided to keep the
factory coolant since it looks perfectly clean and had no major exposure to
usage. The owners manual claims the coolant is good for five (5) years or
156,000 miles which ever comes first.
In your opinion based upon your knowledge of chemistry and your practical
experience is there any likelihood of causing damage by not changing the
Thanks for all your replies, especially HLS, I appreciate your
detailed answer, and the fact that you are a chemist. If the orange
coolant won't hurt my gaskets or seals, I will probably stick with it
since I have had it in there for 7 years and everything seems OK.
However, my feeling is that it's probably not all it's cracked up to
be. Are the majority of new cars using the Orange Coolant now ? Are
they likely to do away with the green coolant altogether ?
When I flush, I usually just take the old thermostat out, and then
circulate distilled water through the system without the thermostat,
drain, refill, flush again, and keep going until the water is clean. I
keep the heater on hot the whole time. When I am finished flushing and
I refill with new anti-freeze, I use distilled water to mix with the
anti-freeze. I usually go ahead and replace the hoses, thermostat, &
radiator cap at the same time.
Do you recommend adding a bottle of Chemical flush to the water on the
first flush, to help clean scale, or should I just stick to using
plain water to flush ? I would guess the chemical flush additive is
compatible with the orange coolants. I have always wondered if the
"chemical flush" might actually do more harm than good.
Lastly, is the orange Dexcool anti-freeze the same as the Orange
Texaco anti-freeze I have been using ?
Thanks again guys,
Are the majority of new cars using the Orange Coolant now ? Are
I believe the majority of cars have now gone over to OAT or HOAT
technology. It is a belief, not a known fact.
There are a lot of cars on the road that have thrived on the older
"green" fluids, and I don't foresee their immediate demise, BUT
there are lots of new fluids on the market that claim to be compatible
And they may be.
This may be the path toward eliminating the green fluids (which are
commodity priced....little profit), and going to something with a little
Except for very dirty systems, I see little to be gained by adding a flush
chemical.. If you flush exhaustively to clean water, that is usually pretty
In some cases where you have a lot of oily scum or iron, it might
be worth the effort.
Notice that no additive that you can buy at your FLAPS will help
if you have silicate deposition in your radiator. Silicate is like glass,
and nothing you can buy will dissolve it. It has to be rodded
out, or cleaned with industrial strength chemicals.
I am not totally sure about this. I have heard that Dexcool is a license
from Texaco, but cannot confirm this without researching it a bit.
I believe that since the mileage seems to be quite low, AND since your
is clear and without indication of corrosion by-products, you are probably
to go for a while.
When you start seeing scum, solids, iron rust, etc in the coolant, that is a
good indication that you have problems building.
Breakdown of the corrosion inhibitor package depends on time, temperature,
oxygen contamination, and circulation (shear).
In your case, which is a bit unusual, it would seem that you have not
the integrity of the coolant yet.
There has been quite a lot said about incompatibility between at least
some of the Dexcool formulations and certain plastic seals. Personally
I would take you car back to green, which is actually getting harder to
find. For example, standard Prestone is now a formulation similar to
Dexcool and not at all like the old standards. Peak still offers a
conventional green coolant as do a few others.
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