I received a phone call on this today from a customer in South Florida. We have two sets of directions that circulate throughout the country. We modified the 50/50 mixture of anti-freeze and water the past few years when we noticed that the success rate wasn't really swayed one direction over another. However, if you are in a cold climate where your vehicle may encounter freezing temperatures--- I recommend the 50/50 mixture. --- And a bonus would be a heated garage or heaters placed around the vehicle.
For everyone else that is in warmer climate- It is fine to just use water.--it's easier that way as well.
*Neither the 50/50 mixture (of water and antifreeze) or just water will harm your engine.