The Stovebolt Site Forums The Shop Area Engine Shop Old fuel?

I drove the Suburban to town today and it was running sickly on the way home. The fuel (ethanol)in it was put in around the end of May, so it is over 3 months old. Does this fuel deteriorate this quickly?

Absolutely anytime after 30 -120 days can be a problem ......especially in hot and humid conditions. May in Texas would also likey be summer grade gas but in other regions winter grade gas in summer temps can cause all sorts of problems like vapor lock, hot restart, irractic idle etc

What kind of carburetor are you running? When you say it ran sickly, is it just at idle, or when romp on it, or all of the time? Does it run any better with the choke slightly closed?
I have had more problems from deteriorating carburetor parts, namely YF accelerator pump diaphragm holes from incompatibility with what they are adding to ethanol fuel.
When that happens, the engine runs very rich and I have to pull the throttle cable to bump up the RPM to keep the excess fuel burning so I can make it home.
Carl

I just read:
That 30 days should be max.
Add fuel stabilizer the day you buy the fuel.
The EPA has allowed E15 in some areas. This is no good for motors.
E10 was the initial 10% ethanol allowed.
Use 87 octane or higher.
Due to fuel tanks being vented, the ethanol blend absorbs moisture at a high rate.

(My boat sits for mo.'s but I have Sta-Bil in it.)

More specific internet wiki: Scary stuff.

Gasoline containing ethanol has become the new standard for fuel, and it presents a new set of challenges and work for classic car owners. You’ve got to be vigilant now to ensure a good running engine and prevent damage to your cherished car.

What’s the problem, you ask?

Ethanol, made from corn or grain, is added to gasoline to oxygenate it, replacing the older additive, MTBE. Names for gasoline mixed with ethanol include E10, gasohol, corn fuel, alcohol fuel, and reformulated or renewable fuel.

The key problem is that ethanol absorbs water from the atmosphere. In fact, fuel with 10 percent ethanol absorbs up to 50 times more water than standard gasoline. Older gas tanks found in many classic cars vent to the atmosphere, increasing the likelihood that moisture will be absorbed into the gas tank at a rapid pace.

The end result of water in the fuel is phase separation. The fuel separates into two distinct layers: a thick layer of gasoline mixed with a little ethanol on top, and a thinner layer on the bottom consisting of water mixed with most of the ethanol. And it doesn’t take much water for this to happen–phase separation occurs in a gallon of 10 percent ethanol blend with just 3.8 teaspoons of water.

Fuel Phase Separation Problems

What happens to your car and it’s performance when water causes fuel phase separation?

Reduced fuel longevity: A gasoline/ethanol blend absorbs water until it triggers phase separation. The blend has a 90-day product life in a closed tank, but lasts just 30 to 45 days in a vented tank often found in classic cars. With 10 percent ethanol blends, owners are supposed to replace the fuel in vented tanks about once a month by driving or draining, taking into consideration the humidity in the atmosphere and temperatures.

Lower fuel octane: The ethanol in a gasoline blend provides some of the octane rating. When phase separation occurs, the octane rating of the remaining fuel can drop by as much as three points.

Poor engine performance:The fuel pump could easily pick up a slug of the water/ethanol slurry at the bottom of the tank, interrupting the flow of gas to the engine. This will cause the engine to miss, run rough and possibly stall altogether.

It is a Zenith, Carl. It has an aluminum pump. I didn't think to try with the choke out.

When it started I could only run 60 in OD. It usually can run 75. Before I made it home it would only hold 45 in OD. I took it out of OD and was able to run 60 on home.

I was thinking of adding fresh fuel to it today but after reading Bart's post, I think I'll bite the bullet and drain it. Don't know what I'll do with 8 gallons of bad fuel though.

Put the old gas in a daily driver two gallons at a time ........should be no problem.

Dig a hole, pour it in and burn it up. Nothing wrong with burning it. If you use it in a motor, you are burning it. Pouring on ground without burning is pollution. If you mix with good gas you make more bad gas. Not worth the $20.

Aviation fuel(80 octane) has no alky in it if you can find it.

Ed

Not recommending this procedure to others, but:

I have approximately 4 acres to mow. Start the lawn & garden John Deere on good gasoline, and get it up to temperature. Now add the older fuel. It will burn if the engine is hot, just doesn't start well. With 4 acres, I burn it all out, and then add some good fuel before shutdown. Only once had to let it run with no load for a couple of minutes when it was unhappy.

Jon.

I finally got around to doing something about this. I drained the old fuel and replaced it with fresh. That was indeed the problem. She runs like a champ now.

Thanks for getting back with your cure. I went back to read your original symptoms, and it makes all the sense in the world. Old ethanol fuel has lost the volatile chemicals which are put into the blend to make the alcohol work in the mix.
Carl

Exactly why I don't run Ethanol in anything unless forced to when away from town on trips. We are fortunate to have many outlets "Including Wallyworld" around Oklahoma who sell real gas. It costs a few pennies more but well worth it.