[Mr.ac]

The proper coolant is either the ready mix blue coolant from Toyota, or Subaru's ready mixed coolant.

Here's the deal man,

1. You could buy a gallon of the blue coolant for $40 at the dealership and only use about a cup. Then have it for summer when you'll need to add another half cup.

2. You can buy a gallon of distilled water for $1 and use a cup of it. Then you can have it for the summer when you'll need to add another half cup.

Either way you'll only need about a cup or two to fill up to the line.