Dry Gas/Fuel-Line Antifreeze Still Necessary?

Now that gasoline contains up to 10% ethanol, is it still necessary to add fuel line antifreeze/dry gas (which is basically just alcohol) to the tank in the winter or is this no longer needed now? My truck stays outside 24/7 and it’s going down below zero in the next few days and I don’t want to have any problems. Thanks!

I recall when ethanol first came out in gasoline they said it was no longer necessary. I haven’t heard anything on that since, but I have never used deicer and I’ve not had a problem, even tho I do often let my tank run to a 1/4 or so before refilling. I know they say not to let it go much below 1/2 in cold weather. I could just be lucky so far…


Ethanol is hygroscopic which means it readily absorbs moisture from the air. If enough moisture is absorbed the ethanol and water will phase seperate out of the gasoline. http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html So if you fill your gas tank where the storage tanks have excess water it can result in phase seperation of the ethanol and water.

Todays fuel systems are sealed. Well, they are until you remove the gas cap and start filling the gas tank. There’s a system in the fuel tank called the Onboard Refueling Vapor Recovery system. How this works is, when you stick the nozzle of the gas pump into the fill neck and turn the pump on, the gas despensing out of the end of the nozzle creates a venturi effect in the fill neck where air is drawn into the gas tank to create a positive pressure in the gas tank. This positive pressure then forces the gas fumes and air thru the carbon canister where the gas fumes are collected before the tank is vented to the atmosphere. And if the humidity level is high while filling the gas tank, the ethanol will absorb as much moisture out of the air that it can. Over time enough moisture can accumulate in the gas where the ethanol and water phase seperate out of the gas.

Most fuel system antifreezes contain %100 isopropyl alcohol. The reason being, just like ethanol it absorbs water. The difference is when isopropyl alcohol absorbs water it doesn’t phase seperate out of the gasoline. It keeps the water in suspension in the gasoline so it can be carried off and burned in the engine.

So if there’s enough water in ethanol gasoline where the water and ethanol phase seperate out the gasoline, the result can be fuel line freeze up.


I would assume then that the higher the content of alcohol in your gas the more likely you are to have moisture problems. So E-85 would be worse than the normal E-10 blend?

Tester wrote an excellent post. The only respectful dissention I’ll offer is in regard to the gasline feezeup. The water molecules are suspended in the gas and get burned (turning into vapor) in the coombustion chambers, passed out the exhaust with everything else. It doesn’t congeal and form a cluster of ice and cause the line to freeze up. The fuel line is high pressure (40 psi and higher depending on the vehicle) and sealed. There are also no open areas in the fuel system to allow condensation. I haven’t seen gas line freeze up since fuel injection became common.

Gas line freeze up is really a thing of the past.