What type of antifreeze for 2000 Mitsubishi Diamante?

The thing you should never do is put 100% water. You can buy the 100 percent antifreeze(the green color kind) and just mix it yourself. You shouldn't put 100% antifreeze either, depending on where you live and the usual temperature you drive through. For a more colder area, you would put more antifreeze than water and hot places about 50/50 antifreeze/water.