Motorcraft -Yellow is the correct coolant to use. It can be blended with your coolant system's current coolant. However, it is best to drain the coolant system and refill it with Yellow. I put a 3/8" i.d. hose onto the petcock to avoid having the coolant spatter over the front part of the frame. Be aware that if you buy Motorcraft -Yellow concentrate from Amazon, you very well might receive the 50/50 diluted type. This happened to me twice this past summer, each time using a different vendor.