When servicing any of the cooling systems on the these vehicles, which includes the High Voltage Battery Assembly, pumps, reservoirs, hoses, air separators, radiators, PIM, engine or heater system it is important to use the proper coolant and water mixture.There is a TSB for it. I can confirm, fill to the TOP of that black label. Why? It helps prevent the SHVCS message from setting when not actually needed. Make SURE you use the correct dex-cool, the one with DEIONIZED water.