Would you run 5-year-old gas in your emergency generator?

Back in January 2011, my lovely bride Jojo and I sold our home and moved into a new R.V. It’s a 42 ft. 5th Wheel Toy Hauler. On the way to our first RV Park, I put 30 gallons of gasoline into the onboard fuel tank used to run our generator.   A week later I added double the recommended amount of Stabil. Note that the manufacturer of Stabil only guarantees safe fuel for two years by doing this.

Now I know I am going to catch some flak by telling everyone this but it’s the truth and I completely own up to it. For the first two years, I only test ran my generator 3 times. After that, I presumed the fuel had gone bad and didn’t want to use it. Another year passed and I had a company try to remove the gas but they were unable to get a hose down into the tank to pump it out and there is no drain. So the gas just stayed there.

This last Tuesday we had a power failure. After about a half hour waiting for the power to come back, and without the Air Conditioner the temperature inside rose to 94 degrees, we decided to try to fire up the generator. I had my doubts about the gas but Jojo sniffed it and said it was good. Now Jojo is overly sensitive to hydrocarbons and has the ability to walk into a garage and smell bad gas. If she says it’s good (or bad) you can bet on it.

So we hit the Prime button till the light came on and then hit the Starter. Nothing. The generator wouldn’t start. Wouldn’t even turn over. Dead battery? Yes, it too was original, and 6 years old. We decided to jump it off the car. After giving the battery some time to charge we said a few prayers, crossed our fingers, and after hitting the Prime button pressed the Start button.

Good Golly Ms. Molly. The generator not only fired up but it ran for nearly an hour without a single hiccup before the main power came back on and we shut it off . Seems the gasoline was still good and the battery was not dead, it just didn’t have the amperage to handle cranking the generator.  The AC had cooled the RV back down to 84 degrees.

An hour later the main power went off again so we repeated the process and ran the generator for about another hour before power was restored and we turned it off again.


  1. Stabil is not just good for gas storage it’s great.
  2. Get a new battery.
  3. Test run the generator on a regular basis.


  1. SpudWeb says:

    I’ve had a 5 gallon can of gas that I have used in my lawnmower for the last 4 years without re-filling, still using it this year so far. I never added any STABIL or other agents, it’s simply the gas straight from the pump and it has worked the same every year since the day I filled the gas can. So YES, I would trust five year old gas (so long as it had been in a shed or otherwise protected from the elements and did not have visible contamination) in an emergency situation.

  2. PatrickM says:

    Always use Stabil and gas treatment/carbcleaner additives, additionally, I run the genset every four months. I usually cut 2×4 scrap into scraps with the circular saw for the load test.

    If you are looking for a gen set, I recomend you get one with a fuel cut off between the fuel tank and the carberateur, when you are done using the genny you turn off the fuel supply and let it run out of gas. Keeps the carb from getting gummed up with stale gas.

    • Back during the run up to Y2K, I bought some gas to have on hand. No Stabil, and I stuck it out behind the shed. Four five gallon containers with just a tarp over it. Promptly forgot about it. Found it four years later, and decided to dump it into my truck. Truck ran fine! No problems at all. I keep 23 five gallon containers on hand for my generator, and every couple of weeks I dump two containers in my truck, refill them, and rotate the rest. Have never had any problem when we needed our generator. I do put Stabil in it now.

      • PatrickM says:

        Did the fuel have the common ethenol addition to it?

        I don’t know for sure but could the ethanol additive help keep fuel fresher? Alcohol mixes with water so it will “burn” and causes less sputtering of the engine.

        Could the tarp’s ‘shade’ have kept fuel from breaking down from UV?

        I think there may be more variables in fuel breaking down than age. No, I am sure no scientist type, but I think there may be some easy explanations.

        • Ethanol wasn’t common until after 2003. Before then MBTE was used. Ethanol is terrible for gas storage, because it is hydrophylic, and will absorb water from the air. Given enough time, that water will separate out and you will have water floating in your tank.

          If you have ethanol gas, keep it in something airtight and pressurized, like a jerry can, to keep it from accumulating water.

  3. WalkAndTalk says:

    I always use double Staybil. A couple years ago I filled the 25 gallon gas tank on my van (I wanted to refresh my fuel stores) with 4.5 year old gas that had Staybil in it. The van ran just fine.

  4. Interesting. I’ve got a Jeep Grand Cherokee that’s just sitting in the in-law’s yard (for reasons) that I’m probably going to end up selling since the transmission is shot. Again.

    One of my fears has been the gas sitting in the gas tank. I put some Stabil in there when the tranny went, because I knew it might be a while before we could do anything, but that was a couple of years ago now and I was worried.

    I’m a lot less worried now.

    • WalkAndTalk says:

      Hopefully when you added the Stabil you were able to get it thoroughly mixed with the fuel in the tank and was then able to get the fuel flushed through the entire fuel line and carb.

      • About all I could do was run the engine a little while to get it through the system.

        Better than nothing I guess.

        And don’t get me wrong, I’m still worried. Just not as much as I was. 😉

      • Elriker says:

        Why mix the stabil up in the lines. As I understand it, Stabil has more the effect of floating to the top of the gas and leaving a layer that allows little of the gas to evaporate, thus sealing it off from the atmosphere more. In this way it stay good. Like those here who comment on gas cans being 5 years old and working. I too have gas over five years old in a plastic gas can that is still ok without any use of Stabil. It was well sealed and had little air left in it. It appears that is what kept the gas good. That and storing it in a very cool place where temp did not fluctuate drastically.
        I have had gas stored 3 years in a generator get iffy on me even though I used Stabil. But note that I only filled the generator tank 1/3 and it sat in weather. It kind of gunked up as well in the lines and I have heard that was most likely because Stabil was used and sat in a harsh environment exposed somewhat to heat, more so than if it was in an auto gas tank where at least shade would had helped mean out the temps.
        If you have gunked up gas lines, and can get most of the gas out of the tank, try Seafoam in the gas. That is the best line cleaner I have used. It will also kick out a lot of gunky crud build up in the cylinders. But beware, that stuff smokes like crazy.

    • Marknmomtana says:

      But you still have the Keep, I’d be worried

  5. I keep 100 gallons of gas on hand and change it out every 12 months. Been doing this for over 7 years now and never had any problems using it in the cars.
    Once I messed up and kept gas in my generator for nearly four years and it would no longer work (with additive).
    People who say gas doesn’t last long haven’t really tried it. It keeps just fine for 2 years and more with additive. At least my real world experience.

  6. The only problem I’ve had with long term gas storage is mixed gas, it holds just fine in cold weather but during hot weather after six weeks or so it’s varnish.
    I’m a firm believer in converting gen sets to propane then keep a 25 gallon tank on hand, indefinite storage, no end of life there.

    • CPA Prepper says:

      Roger that. I invested in a tri-fuel gen set. Propane, natural gas or gasoline.

      As long as Atmos keeps pumping gas, I’d rather use their inventory than mine.

  7. TexasScout says:

    Just make sure you don’t get gas with Ethanol in it. You will be fine.

  8. It may be useful to know how gas goes “bad”. Gas is a blend of a lot of hydrocarbons. It’s engineered (nowadays) to burn at exactly the right octane while releasing the least amount of byproducts.

    To get the octane (the amount of energy in the fuel) to the levels needed in high-performance car engines (because even the one in your little hatchback is “high-performance” as far as engines go) up, there are a lot of volatile hydrocarbons used. That’s why gas smells so strongly — those volatiles are literally evaporating into the air.

    So, the longer you store gas, the more of those volatiles evaporate, and the lower the octane goes. Gas doesn’t so much go bad in the sense of going rancid as it just loses octane. As it loses octane in your car, your car runs less efficiently, and you’ll hear it starting to knock. (You might not hear it, because modern engines are designed to detect the knocking and adjust themselves to eliminate it — at the expense of efficiency.)

    The upside of this is that your generator and small engines are likely to be much more tolerant of sub-octane gasoline. That means that old gas that wouldn’t be good to run in your car is more likely to be OK in a (small) generator. (A whole house generator is more like a car engine, and probably less tolerant.)

    All of this brings us back to STA-BIL and PRI-G. These stabilizers do a lot of things (they prevent algae growth, for example.) The main thing they do, though, is replace the volatiles that evaporate out of the gas. That is why PRI-G says that you can add it to old gas and it will restore the gas. It really is — because it is replacing those lost volatiles.

    So, in an actual emergency, try the old gas. If the gas won’t run, dump some more stabilizer in it (and maybe an octane booster from the local auto parts store) and give it another shot.

  9. You dodged a HUGE bullet!!!! Sta-Bil must be a lot better than advertised (or due to the varying quality of gasoline they only feel they can guarantee the lower amount of time). The simplest way to fuel a generator for long term storage is propane. Propane does not go bad when stored and propane powered engines run cleaner. I have propane powered gensets up to the 40KW level for transmitters that are out in the middle of nowhere for just these reasons. Gas is OK for the homeowner with a little portable set, but not worth a darn for long term storage. I have gas, natural gas, propane, and diesel gensets under my care for radio stations. Each has their place and each has their limitations. Knowing this and planning around it is key to emergency operations.

  10. Howard J Mccarter says:

    I would advise using STA-BIL 360 for ethanol gas.

  11. mom of three says:

    When we bought a new lawn mower, for my mother’s day present last year, I only put real gasoline in it. We paid more it was worth it. The lawn mower, we had before finally died due to the 10 percent ethanol, they add those smaller engine’s can’t use that gas, they putter, gums up the spark plugs, and they eventually stop working. I’ll have to ask the hubby, what type of gas they use in the home generators, he just hooks them up electrical, I would use real gas if it were our set up.

    • Babycatcher says:

      That ethanol really messes up the diaphragms and othe soft plastic/rubber parts in a small engine. My hubby rebuilt every small engine we had: gas weed eaters, water pump, generators,tiller, drill, and a few other things. He replaced the carbeurators and we only use pure gas now. This info is good to know.

  12. The things I learn on this site…A humble thank you!!!

  13. Curley Bull says:

    As Phelps stated, the most combustible portion of gasoline will evaporate. Notice the smell when you are filling your tank, that’s the more combustible portion already evaporating. Over the last 45 years or so, I’ve had some experience with trying to store gasoline and I did learn one thing. Whether you use additives or not, you MUST use a completely sealable container. Fill not to the full mark, but leave as little air space as possible and be DAMN SURE the container is SEALED TIGHT and NOTHING can evaporate from it! Every 60 days flip the container 180 degrees to prevent anything form settling to the bottom and starting the varnish effect. I have used some rather old fuel and when it would not start the engine, it would run the engine if I use starting fluid or fresh gas to get it started. However, when I finally acquired the proper type of containers and followed this advice, it truly stayed good much longer. I have used some I know was at least 5 years old without any problems. BTW, I would suggest using one of the additives just to be a little better off . . .

    • TexasScout says:

      I have heard that the best way to store gas is in the “NATO” cans. Not the copies but the originals. I would think that steel 55 gal drums would work well also. You must also keep them cool(ish) if you want the best results.

      The problem is that gas has a natural “vapor pressure”, so you need to store it under pressure. It’s not much, just a half pound or so (when it’s cool) to several pounds (when it’s hot). The “light ends” as they are called in the industry, can work there way out of the smallest cracks.

  14. Thank you for sharing. For the record I use: https://www.amazon.com/dp/B005JP16TA?psc=1&smid=A3VDBPE82S43CG

    This has rejuvenated gas that is 17 years old. Yep, great stuff and I won’t be caught without it.

  15. I store about 75 gallons of gas. 45 gallons I keep in 5 gallon cans with stabil. Once a year I run it through my truck and refill. The other 30 gallons I use fast enough that I don’t bother stabilizing. Here is something I R learned about ethanol blended gas. Ethanol eventually evaporates from the gas. If you’re using 10% ethanol gasoline,in time ( as little as two months in the summer) you’ve lost 10% octane in your gas. So if you bought 87 octane,after a couple months it would only be 78.3 octane.

  16. Would say you just lucked out. Stabil probably helped. Sometimes I think varnish collects and when it reaches a certain point you have problems. Best solution run gas out periodically esp if things are going to sit. Would double stabil in those situations. Did that with a boat for several years with no problem. Again best run it out if possible. Stabil or PRI-G if know it is going to sit.

  17. Aussie Prepper says:

    I store my petrol in 5 gallon fuel certified plastic containers and some in the older metal jerry cans. I have a lot of Stabil and Pri-D on hand but I dont use it as I rotate my gas into my truck every 3 months or so. I will only stabilize my fuel WTSHTF – pointless stabilizing any fuel that will be used within a year.

    Standard unleaded (no ethanol) has a life of at least 12 months without additives. BUT – and this is a BIG BUT!!! Do not store gas with ethanol in it as it’s life is MUCH shorter for 2 reasons,

    1. Phase separation – the ethanol separates from the gas and falls to the bottom. Once phase separation occurs you cannot remix it. Ethanol is very high octane. As it falls to the bottom enough will eventually collect to give your engine a drink of pure ethanol which it wont like. Ethanol blended fuel is OK as long as you are using it up often – if you use a tank of gas weekly say, you wont have a problem.

    2. More importantly Etahnol is hygroscorbic – it absorbs water. Every day the breather on your fuel tank lets out a bit of air when it expands and sucks some in when it cools in the day/night cycle. Is only a tiny amount but that air getting sucked in has some water vapour in it depending on the humidity where you happen to be. It too collects in the bottom of the tank. Sooner or later your engine will get a drink of water and it is a full pull down to rectify.

    Premium unleaded stores even longer 2-3 years minimum without additives – dont ask me why, I dont know but my research confirms this to be the case.

    I have used unstabilized fuel (no ethanol) in carburetted outboard motors that had been mixed with 2 stoke oil and was at least 3 years old with no problems and no discernible loss of performance. Two strokes are a much simpler engine. Use a bit more fuel than equivalent 4 strokes but SOOOO easy to work on and fix if something goes wrong.


    PS – just to emphasize, I hate ethanol blended fuels with a passion and refuse to buy it.

  18. I also run mowers, chain saws, and vehicles with older stored gas. It was stored with double the Sta-bil, and when I fill the tanks or mix the 2 cycle gas, I pour in about an ounce of octane booster. You cannot buy gas around here without the ethanol, so the octane booster is next best thing to be sure the gas works well. And it does.

  19. Crazy Joe in South Jersey says:
  20. Apollyon says:

    Only a fool would run an RV generator only 3 times in two years, they should be exercised every month for at least an hour under 50 percent load. Exercising the gen set drives off moisture, re-lubricates the engine and generator slip rings. The result is better starting, and more reliable operation and longer engine life. I replaced my Onan 5500Watt 50AMP and it cost including installation $5,100.00 so if you are so cheap with the gas and the exercising of the generator I am sure you don’t want to pay for a new generator. The above instructions above are straight out of the Operator Manual for a 5500 Watt 50 Amp Onan generator.

  21. Jonathan delPozo says:

    The corn alcohol used to make the additive will simply evaporate over time. I have used Stabilt for years. Example, my old 2 stroke snow thrower, sat with very–very old gas infused with Stabilt and it fired right up. Key off, choke twice, key on then if fired right up. I keep several Jerry cans of gas on hand through the year as emergency fuel and use Stabilt in it. I just follow the direction and add perhaps 10 % to the mix. When we had a motor home, I pickled the fuel supply as it usually sat over the winter months. No problems firing up. Even the genset had mo problems. So is it worth while?- – – I think so. I think its well worth the money for peace of mind.

  22. So just wondering. No one talks about about a 500 gal tank.. I use Pri-g or Pri-d. Seems to work. Any help here? I use to run stabil but think this work much better

  23. Chuck Findlay says:

    I would add a trickle charger or a small smart charger to the generator, Smart charger being the better choice as it tops the battery off and then turns off the charge and only turns it on again if it senses the battery needs it. But either one would keep the generators battery topped off.

    Another option is a small solar panel, 5 to 10-watts should do it (and a charge controller) to keep the gen batt topped off.

    Without the charge controller you may cook the battery dry. A small charge controller is like $15.00 at West Marine, I have a few of the small ones for a few stand-alone systems I have.

  24. Old gey guy says:

    Many years ago Bell Labs ran a study of generator reliability. They came up with 1 hour, once a week, under load. All The Bell telephone companies switched to this schedule. I keep 2 55 gal drums of gasoline and use StaBil and rotate it every year. I use a couple of bathroom heaters for a load when I exercise my generators.

  25. Old gey guy says:

    fatfingured name it’s old GREY guy

  26. Good info on the fuel. For myself, I’ve taken my Generators after initial test running and put them in layup. No fuel in the tank or fuel lines. Original oil was replaced with synthetic. Annually I hand turn them over to reassure myself that nothing has frozen up. Now after 10 years these generators both worked after firing them up every five years. The hoses get a coat of Silicone Grease to prevent dry rot. I also made up parts kits for the just in case event. I haven’t used the Sea Foam but it sounds like a good idea to improve longevity. I’m also looking at making up a couple of Propane conversion kits just to be more flexible. I live in a dry low humidity area so the gen set itself shows no rust. If I lived in a humid area I’d use electrical silicone grease on parts of the gen set.

  27. Mechanic says:

    Fuel goes bad due to outside influences ex water, alcohols, crap in the tank and the additives the fuel companies add to the fuel prior to sale. I’ve had fuel last years, I’ve had fuel go bad in just a few months, I’ve had bad fuel right from the gas station.

    generators have become very popular in my area as we have had prolonged power outages in the last few years. As a mechanic, my advice to friends and family is don’t store fuel in your generators. Remove the fuel line from the carburetor and drain the generators tank. Leave the fuel line off the carburetor. This will allow any residual fuel to evaporate from within the carburetor float bowl. The majority of times when small engines fail to start its from the float bowl getting gumed up.

    Follow the rubber line from the fuel on/off switch done to the carburetor. The line is usually held in place by a compression hose clamp. Squeeze the clamp with needle nose pliers or the like and pull the line off. Store it in this manner + using stabil or the like and it’s highly unlikely you will have problems.

  28. Great article and comments! I have my generator in a small purpose built shed. It’s a dual fuel generator that I have connected to a 500 gallon propane tank. However, in cold weather you have to start it on gasoline first. So I keep 2 55 gallon drums of gas behind the shed. I do use Stabil, and I’m always pulling fuel out of one. When the first barrel is empty, I switch to the other, and put the empty in the back of my truck for refueling. I always dump the fuel out of the tank AND the float bowl of the carburetor on the generator after testing or use. And while testing, I always make sure that it runs well on propane. I’m not perfect about it, but I try to test it every couple of months.
    As far as the starting battery goes, I keep a 5 watt solar panel on the south facing wall of the shed, which ensures I always have a fully charged battery ready. Also, a battery kept charged will usually last 2-3 times longer than one not maintained. In the winter, I move my lawn tractor and motorcycle batteries out there and connect them with short jumpers. It’s awful nice to know your equipment and toys will start when needed!

  29. I never use gas containing Ethanol except in my vehicles which is turning the gas over rapidly (using it up quickly). I use Ethanol free gas for all other uses and also add a fuel stabilizer (Star Tron Enzyme Fuel Treatment). Doing this I have had no problems in any of the apparatus and implements except in a pressure washer that sat unused for 3 1/2 years. It cranked first pull after I took the carburetor off and cleaned it and place gas around 18 months old in it.

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