2010 Toyota Highlander Owners Manual - Page 465

4-3. Do-it-yourself maintenance Coolant The coolant level is satisfactory if it is between the "FULL" and "LOW" lines on the reservoir when the hybrid system is cold. Engine coolant reservoir Reservoir cap "FULL" "LOW" If the level is on or below the "LOW" line, add coolant up to the "FULL" line. 440