Can I use the new blue colored Subaru Super Coolant in my pre 2008 Subaru? My edited for clarity response from SOA when I asked this question on 5/29/2008 is below.

We can only recommend that you use the coolant that is recommended for your pre 2008 Subaru. This is because we have not tested or researched using the Super Coolant in previous year models.

Best wishes,
Nancy Quinn
Subaru of America, Inc.
Customer/Dealer Services Department

What types of coolants are available? Ethylene glycol (EG) and propylene glycol (PG). PG is a newer coolant and can either be marketed as one of the new “long life” coolants or “environmentally friendly” coolants. Performance characteristics between the two types are fairly close, so either would be fine for use. PG coolants could be considered to have a “slight edge” based on comparative data though.

What about coolant enhancers? Coolant enhancers are made by several different companies and have several different uses. The main use is to provide increase surfactant action of the water/coolant mix. Surfactants allow a better contact between the coolant and the engine wall surface, which aids in the heat exchange process. Enhancers are fairly inexpensive, and may bring down the temperature a few degrees. These products tend to overstate their claims though. Actual temperature reductions are significantly less when used with coolants. They often advertise “minus XX degrees” on their packaging, when in fact these figures come from using straight water instead of coolant. When used with coolant, temperature reduction of enhancers is greatly reduced.

Should I use tap water, deionized water, or distilled water when mixing? Best waters to use are in this order:
1. Deionized water
2. Distilled water
3. Tap water

Never use straight deionized water in a cooling system, as it by itself, it is VERY corrosive and caustic.