Toyota Prius C 2011 Owner's Manual page 332

NOTICE
■
Do not use any fluid other than washer fluid
Do not use soapy water or engine antifreeze instead of washer fluid.
Doing so may cause streaking on the vehicle's painted surfaces.
■
Diluting washer fluid
Dilute washer fluid with water as necessary.
Refer to the freezing temperatures listed on the label of the washer fluid bot-
tle.
4-3. Do-it-yourself maintenance
4
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