If you're adding coolant or replacing it without flushing the system, it is important (mixing dissimilar additives could lead to undesirable consequences - sedimentation, jelling, etc..)
If you're completely replacing the coolant and doing a chemical flush of the system, it's not essential to use HOAT coolant.. any universal long life antifreeze will work just as well in cooling the engine and will have similar corrosion protection..
Coolant: Zerex G-05 HOAT, a Valvoline product, is available at WalMart here at a reasonable price. The Ford version is yellow, the Chrysler version is orange.
HOAT = Hybrid OAT, ie it is OAT with some silicates in it, not a big deal if considering PEAK or Prestone all vehicle extended life coolants coolants (these are OAT).
I ran the Original Green in my 2002 for a couple of years with no problems. The trend now days is low to no silicates and for the coolants to last for 5 years. So, HOAT is a low silicate coolant and OAT has 0 silicates. Neither have phosphates.
Water: Why take a chance on tap water although that may be what you get if done at a repair shop? Distilled water is not expensive and demineralized water is even less expensive at about $5.00 for 18.5 litres/5 US gallons.
Interesting enough, even Original Green can be low silicate and long life these days. Take Zerex Original Green for example @
http://www.valvoline.com/pdf/zerex_original_green.pdf It is low silicate (<250 ppm) and long life (5 years/100,000 miles).
Zerex G-05 HOAT states typically < 240 ppm silicate @
http://www.valvoline.com/pdf/zerex_g05.pdf Go figure on that miniscule difference when compared to Original Green.
Can't go wrong with Zerex G-05 HOAT and demineralized water. If doing a complete replacement, I would also take a look at PEAK Lifetime antifreeze, depending on how much longer I planned on owning the vehicle. Peak seems to be very competitive and readily available here.
You can blame the Europeans for this HOAT stuff. That's where it all started.
"HOAT" (Hybrid Organic Acid Technology) antifreeze is usually dyed yellow but may also be dyed orange or green. HOAT coolants are currently used by Ford, Chrysler, Mercedes, BMW and Volvo. The additive package in a HOAT formula coolant also contains silicates for added aluminum protection. Most of the antifreezes in this category also meet the European "G-O5" specification for hybrid extended life coolant. The service life for HOAT is also five years or 150,000 miles.
The following article @
Home | G.H. Berlin-Windward gives great information on coolants and answers the OP's question very well.
If a customer chooses a different type of coolant than that which was originally in the vehicle's cooling system, the cooling system should be flushed to remove all of the old coolant. This will avoid any potential incompatibility issues between IAT, OAT and HOAT coolants. We have not heard of any horror stories of bad things happening inside a cooling system when different types of coolants are intermixed. But antifreeze suppliers caution against mixing different types. Their advice is to use "same with same."
c/p
