1999 Subaru Impreza Owner's Manual - Page 290

Washer Fluid Concentration 30% 50% 100% Freezing Temperature 10.4°F(-12°C) -4 °F(-20°C) -49°F(-45°C) HG0122 Replacement of windshield wiper blades Grease, wax, insects, or other material on the windshield or the wiper blade results in jerky wiper operation and streaking on the glass. If you cannot remove those streaks after operating the windshield washer or if the wiper operation is jerky, clean the outer surface of the windshield (or rear window) and the wiper blades using a sponge or soft cloth with a neutral detergent or mild-abrasive cleaner. After cleaning, rinse the windshield and wiper blades with clean water. The windshield is clean if beads do not form when you rinse the windshield with water. CAUTION Do not clean the wiper blades with gasoline or a solvent, such as paint thinner or benzene. This will cause deterioration of the wiper blades. 10-34