I have had a LOT of trouble with aluminum engines (Honda) pertaining to coolant issues. My problem was (me being ignorant) I put my "well" water in with the coolant. (very soft, high salt content) It ate the head up completely.

I would spring for the OEM coolant, you only change it once every 60K and it's worth the price. Never put anything but distilled or deionized water with coolant.