Toyota 2013 Prius PHV Owner's Manual page 530

4-3. Do-it-yourself maintenance
Coolant
The coolant level is satisfactory if it is between the full ("FULL" or "F")
and low ("LOW" or "L") lines on the reservoir when the hybrid system
is cold.
Engine coolant reservoir
Power control unit coolant reservoir
464
PRIUS PHV_OM_OM47787U_(U)
Reservoir cap
"FULL" line
"LOW" line
If the level is on or below the
"LOW" line, add coolant up to the
"FULL" line. (→P. 617)
ITO43P111
Reservoir cap
"F" line
"L" line
If the level is on or below the "L"
line, add coolant up to the "F" line.
(→P. 617)