Gas Caps do seal out any condensation from entering the gas tank, despite the arguments here saying they do not

[Moparjoe499]

Most of the time people are putting water into their gas cans and don't even know. Ethanol in fuel contains a certain percentage of water left from the manufacturing process. That water may be stable at 70 degrees but could phase separate at 30 degrees.

Years ago before ethanol people would leave their vented gas cans out and would either condense water from temperature air exchange or just flat get rain in them. Now with ethanol the alcohol makes it it's mission to draw water from the air every change it gets being it from open vent container or other means.

People will leave their gas cans outside and expect their mowers to run. If you use gas out of a can often enough, their shouldn't be any water in the can unless you are getting it from the gas station.

 

[Hammermechanicman]

My 1989 motorhome with a Qjet carburetor sat for 5 years in an unheated barn with E10 gas in it. Fired up and ran fine. I have customers who leave E10 gas in a snowblower for 6 months and it trashes the carb.
I don't know much but I do know ethanol in gas makes me money.

 

[ILENGINE]

People will leave their gas cans outside and expect their mowers to run. If you use gas out of a can often enough, their shouldn't be any water in the can unless you are getting it from the gas station.

But that is the thing. You are getting it from the gas station. Ethanol enriched fuel contains water

 

[Gord Baker]

No it is simply because the moist air that came in cools down overnight.
As the air cools it capacity to hold moisture drops so the water forms droplets & runs down the side of the tank

You are correct Shady. In a partially filled tank, the air does not 'come in' overnight. What air is in the tank remains until more contents is used. Ethanol absorbs water in the fuel and condensate and remains at the bottom of the tank with it. Don't totally empty a partially filled container into your small engine. Always use a funnel with filter to take out the lumps.

 

[Moparjoe499]

My 1989 motorhome with a Qjet carburetor sat for 5 years in an unheated barn with E10 gas in it. Fired up and ran fine. I have customers who leave E10 gas in a snowblower for 6 months and it trashes the carb.
I don't know much but I do know ethanol in gas makes me money.

I have a snowblower in the garage. I have not started it in 6 years. Choked it, pulled it 2 times and it runs. People have water in their gas cans.

 

[upupandaway]

Air contains Moisture. A Fuel Tank MUST be vented to allow fuel to flow out, thus fresh air is being constantly drawn into the tank.

True. Just look at a plastic gas can when temp drops 20deg or rises 20 deg. The gas can shrinks or bulges- that would vent or draw in air if it wasn't air tight.

 

[Moparjoe499]

True. Just look at a plastic gas can when temp drops 20deg or rises 20 deg. The gas can shrinks or bulges- that would vent or draw in air if it wasn't air tight.

And stop leaving your gas can outside.

 

[upupandaway]

And stop leaving your gas can outside.

Thing is, leaving it in the garage has the same effect, just not so bad.

 

[Moparjoe499]

Thing is, leaving it in the garage has the same effect, just not so bad.

It won't make any difference if the gas cap seals or not. If you are using the gas fast enough out of the tank, people don't have to get all anal about water.

 

[CraftsmanFlaws]

It won't make any difference if the gas cap seals or not. If you are using the gas fast enough out of the tank, people don't have to get all anal about water.

From you other long post here, it sounds like you have a lot of knowledge about how gasoline (more, it's the ethanol) attracts water. I don't agree w/you that covering a vented gas cap completely with plastic wrap & then rubber bands won't keep moisture out. It HAS to.

I, unfortunately, thought I bought enough gas to completely fill the tractor tank; but, it didn't & I am a gallon short. I was just tired & cold, & decided to simply leave it this way. According to some of the posts, a tractor gas tank holds such a finite amount of gas, it doesn't make a great deal of difference. Prior, I added Seafoam to the gas, ran it a few minutes, so don't you believe it will prevent rubber & carb damage over the winter?