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lines now, too. This stuff seems to offer pretty much the best of both worlds -- it's not quite as long-lived as straight
OAT, but it is much better behaved in operation than OAT, much like conventional coolant.
“Note that these three different additive packages are not really cross-compatible. No, they won't eat the insides of your
radiator if you mix a little of one in with another in a pinch, but you'll be better to get the system flushed out and a fresh
mix of 50/50 whatever your car needs put back into it.
“If I owned a car that came with OAT or HOAT from the factory, I'd likely stay with it. The anti-corrosion additives,
in particular, leave residues on the walls of the various coolant passages (that's how they work -- the residues coat the
base metal and prevent corrosion), and it's tricky to convert an engine that's been run with one style of package to use
another package and get the full benefit.
“Switching from conventional to OAT, for instance, requires a mild acid flush of the cooling system after removal of
the conventional coolant and before pouring in the OAT if the long-life corrosion benefit of the OAT coolant is to be
realized. Just pouring the OAT in after draining the conventional won't gain the full measure of added coolant life the
OAT marketers (notably Texaco) like to use as selling points.”
Somewhere in the midst of all this, the labelling on the containers of DEX-COOL quietly changed, making far more
modest claims for durability and combatibility.
Quoting from the
Popular Mechanics web site
: “Now let's look at "retrofit" and "drain and fill" and explain what you
can and can't do safely, and a bit of why. If a vehicle has a copper-and-brass radiator, forget a retrofit, says General
Motors, because the organic acid (orange) antifreeze may not provide adequate protection for the lead solder in that
radiator. The Chrysler orange hybrid combination of silicates and organic acids is meant to provide special protection
for the water pump. Sorry, you can buy it only at a Chrysler-brand dealer.
“Prestone believes you can retrofit to its organic acid orange almost any vehicle with an aluminum radiator and cooling
system that has been well-maintained and is in good condition, if you do it right. However, the antifreeze maker
recognizes the possibility of a problem with Dodge truck 5.9-liter V8 water pumps, for which green or yellow/gold
U.S. antifreeze is recommended–if you don't get Chrysler's specific orange.”
A 1998 magazine article quoting Applied Chemical Specialities Co. (a competitor of Havoline) put the retrofit issue
more strongly: “DEX-COOL is an excellent antifreeze to be used in brand new cars in which traditional
phosphate/silicate antifreeze has never been used. However, if any traditional antifreeze has ever been used in your
car's cooling system, it is strongly advised to avoid using DEX-COOL. This is because, short of a dangerous strong
acid cleaning or complete replacement of ll parts within the cooling system, it is physically impossible to remove all
residuals of phosphates and silicates - even with repeated flushing. If DEX-COOL is used in such a system, deposit
formation will be almost instantaneous and will seriously affect your car's cooling system efficiency and performance.
Because most corrosion occurs under such deposits, it will also affect the long-term corrosion prevention in such a
system as well.”
In a more Jaguar-specific vein, Al Askevold reports some problems with DEX-COOL: “Besides the bad report about
DEX-COOL from the radiator shop who did my recore, I could not remove my rad caps without damaging the rubber
seals, and my Tefba filters - I had to remove them and clamp them in a vice to remove the tops. I tried several different
kinds of lubricant on the parts with no effect. I finally flushed the DEX-COOL, I am now using a different brand, so
far no problems.”
WATER: The antifreeze needs to be mixed approximately 50/50 with water, but if you care about your cooling system
you might want to be careful about what water you use. The garden hose may be convenient, but it’s not necessarily
healthy for the car. The biggest problem to be concerned with is dissolved solids, that stuff that’s left in a pot after you
boil water away. Since boiling is often going on alongside the hottest parts of the engine (cylinder liners, head), this
same stuff is left there. As a scale on the metal surfaces, it can insulate them from the coolant and make the cooling
system less effective. When the scale flakes off in chunks, it can find its way into the radiator and plug up some of the
tiny tubes. Finally, the scale is somewhat abrasive, and therefore is not particularly good for the seal in the water pump.