Toyota 2015 Prius Owner's Manual page 546

NOTICE
■
When adding engine/power control unit coolant
Add coolant slowly after the hybrid system has cooled down sufficiently.
Adding cool coolant to a hot hybrid system too quickly can cause damage to
the hybrid system.
■
To prevent damage to the cooling system
Observe the following precautions:
●
Avoid contaminating the coolant with foreign matter (such as sand or dust
etc.).
●
Do not use any coolant additive.
PRIUS v_OM_OM47887U_(U)
8-2. Steps to take in an emergency
I n f o r ma t i o n P r o v i d e d b y :
545
8