18 month old gas in the tank - what to do?

[literatesavant]

I'll start by saying that this question is somewhat academic at this point, because I've now used up most of the gas with no apparent ill effects. But I am curious about others' thoughts on this: I had to store my 1988 Porsche 911 for what I thought would be 6 months, but turned out to be 18 months. Before I parked it, I filled the tank and put in a fuel stabilizer. Over the next 18 months I drove it for short periods a couple of times, and that was it. Now I'm back to being able to drive it frequently, and I had naively thought I would just add more stabilizer to the existing tank of gas and then finish it off at my leisure. Then I discovered that, first, you can't add stabilizer to old gas and expect it to do anything, and second, the stabilizer I used is only good for 12 months. Since the engine seemed to run absolutely fine, and because there was on the order of 60 liters of gas still in the tank, I opted to just try to burn through the rest of it as soon as possible. Some people felt that I should use 1/4, fill the tank, use 1/2, fill the tank, etc., basically diluting the older gas over time. Others felt that I should not dilute it, and just use up all the old gas as fast as possible. But these were just opinions not backed up by anything. My question: does anyone have facts/data about gasoline that would support one or the other of these choices? What exactly happens to gas over longer periods of time? People say it "breaks down," but I'd like to know more specifics just because I'm curious. Thanks!

 

[fitrucker]

If it's premium just drive it to about 2 gallons and then fill up. If it starts and runs normal there is nothing wrong with the gas. If there is problems then you will have to drain the tank and add fresh. Drive easy and don't recommend adding gas until you lower the fuel level.

 

[SC Maintenance]

Old gas slowly looses its octane through oxidization

Non ethanol gas looses it slower. Temperature and how its stored changes the affect as well.

With stabilizer you were likely fine. I would likely have diluted it if I could, but it seems to have worked out fine for you.

 

[k1xv]

I would just drive normally, using it up, unless the car failed to perform as it should. With fuel injection, I believe cars are more tolerant of slightly stale fuel than in the old days of carburetors. If there is any indication of poor performance, add some fresh fuel and drive some more.

With vapor recovery systems, losing the "light ends" out of the gasoline to evaporation is less of a problem than it used to be.

 

[literatesavant]

Oh yeah, I can add a couple of additional points:

I'm in Australia, and the car had 91 RON gas in it - that's the regular/lowest grade here. No ethanol. And, having read that octane will dissipate over time, I did add a bottle of octane boost/fuel system cleaner before I resumed regular driving. The car was stored in a garage, and obviously the climate is normally pretty mild here.

With vapor recovery systems, losing the "light ends" out of the gasoline to evaporation is less of a problem than it used to be.

"Light ends?"

 

[k1xv]

Gasoline is a blend of various naphthas and hydrocarbons. The "light ends" are the less complex hydrocarbons in the mix, such as pentane, that are first to evaporate in an open container of gasoline. Vapor recovery systems capture this evaporation and return it to the fuel in the tank.

Winter gasoline typically has a greater proportion of "light ends" to assist in cold weather vaporization.

 

[slacktide_bitog]

drive it

 

[billt460]

I'll start by saying that this question is somewhat academic at this point, because I've now used up most of the gas with no apparent ill effects. But I am curious about others' thoughts on this: I had to store my 1988 Porsche 911 for what I thought would be 6 months, but turned out to be 18 months. Before I parked it, I filled the tank and put in a fuel stabilizer. Over the next 18 months I drove it for short periods a couple of times, and that was it. Now I'm back to being able to drive it frequently, and I had naively thought I would just add more stabilizer to the existing tank of gas and then finish it off at my leisure. Then I discovered that, first, you can't add stabilizer to old gas and expect it to do anything, and second, the stabilizer I used is only good for 12 months. Since the engine seemed to run absolutely fine, and because there was on the order of 60 liters of gas still in the tank, I opted to just try to burn through the rest of it as soon as possible. Some people felt that I should use 1/4, fill the tank, use 1/2, fill the tank, etc., basically diluting the older gas over time. Others felt that I should not dilute it, and just use up all the old gas as fast as possible. But these were just opinions not backed up by anything. My question: does anyone have facts/data about gasoline that would support one or the other of these choices? What exactly happens to gas over longer periods of time? People say it "breaks down," but I'd like to know more specifics just because I'm curious. Thanks!

If you can run the engine on the gas that's in the tank, then just finish it off to as low of an amount as you're comfortable with, then fill it up with fresh fuel. You don't have a problem.

Gradually diluting it is only prolonging it's consumption. 18 month old gas that has been stabilized should not be an issue. I once left a full tank of heavily stabilized fuel in a lawn mower for over 5 years. It started and burned through it just fine.

 

[CharBaby]

Since your engine runs well with the 18 month old fuel, I would agree with others and say to do what you're currently doing and use up your gas in the tank.
What you did by using fuel stabilizer was the right thing to do prior to storing your car. But, you knew that.
In the future you may want to do an extra step above what you are currently doing prior to storing your 911.

*Use premium octane fuel for you engine (which you probably already do) and possibly use(Oh, IDK) a marine fuel stabilizer just in case you find yourself storing the vehicle for much longer. And maybe slightly overdose the fuel?

I believe a marine stabilizer is slightly better than regular stabilizer??? I believe that's how it is here in the states. We have several different types of stabilizer for different uses.

I've been storing cars since around 1974 and have had good success doing the above. Currently I've been storing the 1980 Firebird in my signature for all of its 43 years(since new) and she runs fine.

 

[literatesavant]

I guess I've always been told that old gas turns gummy or to varnish, so I was worried about gumming up my injectors or fuel filter. Is that not a concern, or just not on this timescale/under these conditions?

 

[Lubener]

As long as the gas doesn't smell like varnish, I would dilute it with some fresh gas and drive it. I have gone as long as 13 months without stabilizer and not having any problems. A full tank will last much longer than a 1/4 tank of gas.

 

[CharBaby]

Just run the car and that old fuel may in fact clean clean the varnish that might have started just while it's moving through the lines/injectors etc. IDK, maybe throw in a bottle of good/well known fuel system cleaner with PEA into the current tank of gas.

 

[JC1]

To the OP, this situation is causing you great anxiety. Leave me the ownership and I'll be by in the morning to take the car off your hands. .

Just drive the car more to use up the old gas and refill it once you're down to a 1/4 tank.

 

[Hall]

and second, the stabilizer I used is only good for 12 months. Since the engine seemed to run absolutely fine

That stuff doesn't evaporate at the 12-month mark. The formulator expects 85-100% "success" by the 12-month mark and after that, it may be 85-90% "good" for 6 months, then 80-85% "good" for another 6 months. It just doesn't stop working. It's fine.... and you say the engine is running fine. Why even go down this rabbit hole ?

My % numbers and time frames are arbitrary too, to be clear, but the premise is the same.

 

[fitrucker]

I guess I've always been told that old gas turns gummy or to varnish, so I was worried about gumming up my injectors or fuel filter. Is that not a concern, or just not on this timescale/under these conditions?

I've used unknown gas in a plastic gas can for years from projects my son was doing. Gas in the cars were in the gas tank for unknown time more that a few years. I assumed it was premium with ethanol. Water is enemy and actually ethanol free gas can't hold water. It will just separate and drop to the bottom. So if you car runs fine just drive until tank is near empty. Hopefully no issues because if there is water then you basically need the whole fuel system rebuilt and cleaned.

 

[spasm3]

Dump a can of berryman b-12 in, and drive it.

 

[kschachn]

What a popular question.

There are several existing threads on this topic, one is currently in progress:

Anyone know of any places that take old gasoline?

I'm going to be syphoning old gas out of a car that has sat for quite a while. To my surprise there is no place in town that disposes of old gasoline. Not a single friggin place as far as hazardous waste facilities go. I'm looking for some ideas on how to dispose of this stuff without...

bobistheoilguy.com

 

[4WD]

I'll start by saying that this question is somewhat academic at this point, because I've now used up most of the gas with no apparent ill effects. But I am curious about others' thoughts on this: I had to store my 1988 Porsche 911 for what I thought would be 6 months, but turned out to be 18 months. Before I parked it, I filled the tank and put in a fuel stabilizer. Over the next 18 months I drove it for short periods a couple of times, and that was it. Now I'm back to being able to drive it frequently, and I had naively thought I would just add more stabilizer to the existing tank of gas and then finish it off at my leisure. Then I discovered that, first, you can't add stabilizer to old gas and expect it to do anything, and second, the stabilizer I used is only good for 12 months. Since the engine seemed to run absolutely fine, and because there was on the order of 60 liters of gas still in the tank, I opted to just try to burn through the rest of it as soon as possible. Some people felt that I should use 1/4, fill the tank, use 1/2, fill the tank, etc., basically diluting the older gas over time. Others felt that I should not dilute it, and just use up all the old gas as fast as possible. But these were just opinions not backed up by anything. My question: does anyone have facts/data about gasoline that would support one or the other of these choices? What exactly happens to gas over longer periods of time? People say it "breaks down," but I'd like to know more specifics just because I'm curious. Thanks!

It can drop in octane - some 104 Octane Boost would help beforehand …

 

[kschachn]

An octane rating loss would not be my first concern with really old gasoline.

 

[4WD]

An octane rating loss would not be my first concern with really old gasoline.

I expected you to come back with that - but it matters on the expensive stuff ~