I'd go with a Lexus/Toyota long life coolant (or equivilent). Have your mechanic inspect the cooling system for any leaks & get hin/her to look at the thermostat & rad cap & hoses. Use distilled water as well & do a complete flush. After that is performed, keep your eye on the fluid level for the next week or two in the recovery tank. Top up if needed, but if your adding a lot in that time, take it back because something is wrong.