Gasoline Shelf Life

[madizell]

Have to be a whole lot of water. Not just atmospheric stuff. High performance/high altitude gas engines have used water injection for generations for power increases. Usually, if there is more water than gas in the gas, it just stalls the motor. Normal aspiration does not draw sufficient water into the chamber to bend a rod, even if all the carb has in it is water.

As for the CJ-7, I think you are good to go. Tank up and forget it.

 

[Lynn]

Not doubting what happened, but I can't see the connection between stale gas and bent rods.

Gasoline contains alkenes (hydrocarbons with double bonds). Over time they react with oxygen. The result is what we usually refer to as 'varnish. '

He said that the 'varnish' in the cylinders had the pistons stuck tight enough to bend the rods.

I'm not sure how many years that engine had sat with gas in it, though.

 

[R_Lefebvre]

I tell them that a lawn mower has only one cylinder and a V8 has multiple cylinders....so if a V8 has bad gas it has other cylinders to help it along it may seem like its running in tip top shape but its not...now if a mower has bad gas you will know it right away since it doesn't have other cylinders to help it along.

That doesn't make any sense. No matter how many cylinders you have, if the gas supply is bad, all the cylinder will run bad.

Anyway, the point that has been missed here is what type of container the gas was stored in. Metal tanks keep gas much much longer than plastic. The lighter components evaporate through the wall of the plastic tank, but can't get through the metal wall.

I generally don't use Stabilizer. I find it's a waste. If the gas sits for a few months, it should be ok. If you are leaving it for longer than that, I don't like to leave any gas in it anyway.

 

[Spikepretorius]

Buddyomine had a sweet '56 truck that had sat a few years with a half a tank. He tried filling the tank with new gas and burning the old stuff. In the process he bent a few rods. Sorry, don't know how old that gas was.

Possibly a sticky needle and seat flooded the combustion chambers. That would bend a conrod.
It happened with a friend of mine. He prepped his megabuck race car at the workshop, took it down to the track, turned the key, and doof. From workshop to track it leaked into the cylinders.

 

[kerry]

When old gas varnished the intake valves tight on my 413, it took lots of blows with a 4lb sledge hammer on to a 2x4 to loosen the valves. Once they were loosened and new pushrods installed, it was back to normal.

 

[motomech]

That doesn't make any sense. No matter how many cylinders you have, if the gas supply is bad, all the cylinder will run bad.

Anyway, the point that has been missed here is what type of container the gas was stored in. Metal tanks keep gas much much longer than plastic. The lighter components evaporate through the wall of the plastic tank, but can't get through the metal wall.

I generally don't use Stabilizer. I find it's a waste. If the gas sits for a few months, it should be ok. If you are leaving it for longer than that, I don't like to leave any gas in it anyway.

Totally makes sense, bad gas is still flammable.So sometimes it will hit and sometimes it will miss. A V8 will have better chance running on bad gas than a single cylinder engine.Take bad gas and put it in a lawn mower and it wont work but take the same gas and use it in a V8 and it will run.It wont run top notch but it will run.

 

[jcbrandon]

anecdotal evidence

I believe one of the concerns with gasoline in a vehicle is moisture. In a damp climate, moisture condenses out of the air in the fuel tank and sinks to the bottom. When you drive the car, these "bubbles" of water get sucked into the fuel pickup and ingested by the intake. This can cause the engine to stumble or stall. One way to combat this is to top off the tank before you store a vehicle. This reduces the amount of air in the tank and so reduces the oppoortunity for moisture to condense out of that air. I have seen this in a sports car stored for months at a time near San Francisco.

On another note, last weekend I pulled two gasoline camping stoves out of storage. They were each put away with about a half-tank of good quality stove gas at least three, and maybe as much as six, years ago. I figured they would be gummed up, refuse to start, and I would have to rebuild them. While stored, they have both been exposed to near-zero winters and summers well over 100 degrees. Both started in the first 15 seconds and ran fine on the stored fuel until I got tired of watching them burn.

 

[RoundOut]

During Hurricane Season, I usually store between 30 and 35 gallons of gas in my generator and plastic cans. At least every few months (3-4) I top off my vehicles with what is in the cans and generator and go fill the cans. This serves to cycle the gas before it has a chance to become "varnish".

One note on the science of gas these days... most gas in the lower 48 has up to 15% alcohol in it to serve as an "oxygenate". It serves to absorb water in a fuel system, reducing the problem of water in your lines freezing in cold temperatures. I don't know if the alcohol is a smaller molecule than the gasoline, which would allow it's vaporous state to pass through the plastic more readily. It may serve to absorb moisture in a can more readily as well, though.

With this much fuel storage, 30-35 gallons, I also tend to use it up when the price of fuel is steadily falling, and then refill it before it rises again (I never catch the top or bottom, but I sometimes get close). I still cycle all cans every 3-4 months when full and make sure my spare gas is available during hurricane season.

[off topic]
On that note, our generator burns about 8 gallons per day and we just had our power turned back on after Ike. It went out at 2:45 a.m. on the 13th and it came back on about 2 hours ago, almost 7 days later. It was costing us about $30/day. Ouch. Thank God for the ability to help friends with ice though. We were able to freeze many gallons and litres of water for friends and rotate their water for ice.
[/off topic]


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[madizell]

Gasoline creates varnish when exposed to atmosphere, from just sitting around. I have never seen valve stems "varnished" as they generally live in an oil bath not gasoline bath environment. I believe the conclusion that bad gas stuck the valves is erroneous.

Similarly, a float valve works in real time. If varnished over time, it would stick shut, not open. Sorry. Seen several totally varnished carbs, but never seen one lead to stuck valves or hydro-locked cylinders Something else was at play.