TOYOTA 2011 Yaris Hatchback - Manual (Page 281)

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4-3. Do-it-yourself maintenance
NOTICE
n 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.
n Diluting washer fluid
Dilute washer fluid with water as necessary.
Refer to the freezing temperatures listed on the washer fluid tank.