I did this not too long ago. I bought a gallon of the Toyota Red coolant, $15. It took a gallon of distilled water and the entire gallon of the Toyota Red coolant to refill the system. I just did a 50/50 mix. You can do a 70/30 of coolan/water mix if you want, but I think 50/50 is adequate. Use a seperate gallon jug to premix the coolant and water, then pour it in. They make a special funnel that snaps into your radiator cap location to refill the system, it allows you to fill and let air out of the system at the same time.