2012 Toyota Avalon Owners Manual - Page 391
2012 Toyota Avalon Manual
Page 391 highlights
4-3. Do-it-yourself maintenance Engine coolant The coolant level is satisfactory if it is between the "F" and "L" lines on the reservoir when the engine is cold. Reservoir cap Full Low If the level is on or below the "L" line, add coolant up to the "F" line.