Lexus RX 450h 2010 Owner's Manual page 485

4-3. Do-it-yourself maintenance
Power control unit coolant reservoir
Coolant selection
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Only use "Toyota Super Long Life Coolant" or similar high quality ethylene glycol
based non-silicate, non-amine, non-nitrite, and non-borate coolant with long-life
hybrid organic acid technology.
U.S.A.: "Toyota Super Long Life Coolant" is a mixture of 50% coolant and
50% deionized water. (Minimum temperature: -31°F [-35°C])
Canada: "Toyota Super Long Life Coolant" is a mixture of 55% coolant and 45%
deionized water. (Minimum temperature: -44°F [-42°C])
For more details about coolant, contact your Lexus dealer.
If the coolant level drops within a short time of replenishing
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Visually check the radiators, hoses, engine/power control unit coolant reservoir
caps, drain cock and water pump.
If you cannot find a leak, have your Lexus dealer test the cap and check for leaks in
the cooling systems.
484
Reservoir cap
"FULL" line
"LOW" line
If the level is on or below the
"LOW" line, add coolant up to the
"FULL" line. (→P. 634)