I have been told most gasolines have an additive to remove water??
That is kind of a complex question actually. At the supply end of gasoline they sometimes put additives (demulsifiers) in to make the water fall out of gasoline so they can draw it off the bottom of the supply tanks. Hydrocarbons will absorb a certain amount of water and keep it entrained at different temperatures (all based on the saturation point). Most gasoline now has ethanol added at the truck rack before it goes to the gas stations. Ethanol will help the gasoline absorb water. A little bit of water isn't going to hurt anything as the car will just run it through with the gasoline, however large amounts of water can become problematic. If there's enough water in the gas to fall out and start forming water puddles on the bottom of your tank you can have a problem with your car trying to suck pure water through the system which obviously won't work too well. By adding a gas line drier to your fuel you will help it absorb the water and pass it on through with the fuel. If there's too much water you will need to try to drain the bottom off of your gas tank to remove it. This is the reason I tell everyone I know NOT to buy gasoline at a station where a truck is dropping fuel. All of the water that had fallen out of the fuel to the bottom of the tank is now being stirred into the rest of the gasoline and may take a couple of hours to fall back out. If you buy gas while the truck is discharging you stand a chance of getting some of the water that was on the bottom of the tank. They will tell you there's filters in the pumps to separate out the water before it gets to your car but they are not 100% effective.
They do, but it isn't enough to much to remove water. The alcohol they add is strictly for adding oxygen to the fuel, making the engine burn a little cleaner. If you have a water issue, it is best to drain out the tank and put in fresh gas. Trying to run it thru the engine by adding alcohol from a bottle (gas dryers) will damage your fuel pump.
If you live in colder climates (This is the case in New York.) then Ethanol is blended with the Gasoline. One of the things this does prevent the typical wet gas problem caused by condensation. If you tank is actually leaking in large amounts of water then the Ethanol will not even come close to offsetting the water.
