Don't risk it trying to use some random other type of coolant. We've always found the best to be the original Toyota factory fill stuff! Toyota has discontinued their fully concentrated coolant, so only 50/50 mixture is available anymore. We have no way of getting 100% coolant

If you live up north or anywhere that it snows, we recommend keeping a 50/50 mixture or so in your Supra. In southern states that don't see freezing weather, you'll often see people running only 35% coolant in their system and the rest distilled water, for the best performance.