21
$\begingroup$

Looking for a way gasoline can last more than 3-6 months?

Going off the simple zombie apocalypse scenario, I want a way to find vehicles and drive them after they have sat for 2,3... x number of years? Another way might be to “preserve” gas if I was to collect it right after the “event”.

$\endgroup$
11
  • 8
    $\begingroup$ Depends on what you call gasoline. The currently available various commercial products sold under that name are indended to be burned within a reasonably short time. But in practice, gasoline remains usable for considerably longer than three months; I have had practical experience starting an engine after four years of neglect, and it worked with the gasoline in the tank. $\endgroup$ – AlexP Feb 19 at 3:08
  • 1
    $\begingroup$ @AlexP not that may have been ethanol free gasoline or stabilized gasoline, normal modern gasoline has an awful shelf life, I don't even bother filling my backup generator anymore and just rotate out hand tanks becasue the fuel becomes worthless so quickly. $\endgroup$ – John Feb 19 at 6:17
  • 7
    $\begingroup$ Gasoline DOES last for years. Once upon a time, when I was broke and gas was expensive, I drained gas out of cars that had been in a farm junkyard for years, and used it in mine. No noticable problems. And the gallon can I keep for the chainsaw lasts a couple of years. $\endgroup$ – jamesqf Feb 19 at 16:44
  • 1
    $\begingroup$ Ah, the myth of bad gas. Thee is no such thig as bad gas, just bad engine design. $\endgroup$ – Justin Thyme the Second Feb 19 at 18:56
  • 1
    $\begingroup$ Due to lack of driving over the past year, I just filled up one of my cars for the first time in nearly a full year (something like 11 1/2 months). It was still driving fine on the old gas. I've used gas before that was sitting in cans for years and not had issues. too. Gas going bad in just a couple months appears to not actually be a thing. $\endgroup$ – Brian Knoblauch Feb 20 at 19:03
51
$\begingroup$

The real-world answer is fuel stabilizers.

The more entertaining answer is that your colony has enlisted a pyromaniac who is slowly building a gasoline re-refinery near the edge of town. He collects bad gas from anything with wheels, knows all sorts of chemistry, has several engines that very loudly test the octane rating of his fuel products and call in zombies from several miles away, and tries to ration himself to one explosion per week. Gas that doesn't make the cut gets reprocessed into napalm for ... stopping zombies. And practicing stopping zombies. His scars are helping the local nursing student develop experience in sterile dressings...

$\endgroup$
6
  • 1
    $\begingroup$ An amusing and well thought out answer. +1 $\endgroup$ – Enthus3d Feb 19 at 14:09
  • 1
    $\begingroup$ napalm would be basically useless for stopping zombies, they don't need to breath which is how napalm kills, by denying oxygen or scorching the lungs. $\endgroup$ – John Feb 19 at 16:54
  • 6
    $\begingroup$ @John Napalm usually kills humans through asphyxiation, but it’s still very nasty stuff even if you don’t need to worry about breathing (1000C is hot enough to cause potentially lethal external burns in a very short period of time). If we assume ‘Walking Dead’ style zombies that still need mostly usable muscles to be able to move, long-term exposure to the heat from napalm would cause them serious mobility issues because of what it would do to muscle fibers. $\endgroup$ – Austin Hemmelgarn Feb 19 at 17:14
  • 1
    $\begingroup$ Yes it depends on your flavor of zombie, how much real biology it obeys. $\endgroup$ – John Feb 19 at 17:15
  • 1
    $\begingroup$ BBQ zombies.... $\endgroup$ – manassehkatz-Moving 2 Codidact Feb 19 at 18:28
17
$\begingroup$

Gasoline itself isn't the problem. Originally, gasoline was a naturally occurring or easily fractionated mixture of hexane, heptane, and a little octane (usually with trace impurities of pentane and nonane and various isomers). Gasoline engines made as late as the 1930s ran on this mix straight out of the oil well in some locations (Pennsylvania, for instance), or straight from the distillery with no additives needed.

Then came high compression, requiring higher levels of the heavier fractions -- "octane number", as much as 100% octane -- for resistance to preignition. And then even higher compression, and leaner mixtures, and more spark advance, all in pursuit of higher power and efficiency, requiring octane numbers, in some cases, well above 100 (one grade of aviation fuel is 115 octane).

Obviously, you can't make a fuel with more than 100% content of octane, but over the period from 1930 to 1960 other additives (tetraethyl lead being the most infamous) were discovered that increased the effective octane number -- now defined in terms of "knock resistance" without actually requiring the presence of octane. It's these additives that are mostly responsible for aging effects on stored gasoline -- some are more volatile than hexane and so preferentially evaporate off, some are more prone to low temperature oxidation, which leads to things like "varnish" formation. All of them make the fuel more prone to dissolve stuff from the tanks and fuel lines.

Bottom line is, gasoline will still burn no matter how long it's been stored (in underground tanks, for instance), it just won't work well in modern engines. Solution: don't use modern engines, find old technology to burn your old gasoline.

Any common car engine built before the Second World War, and most modern aircraft engines, will run fine on additive-free gasoline, including old gas that's been stored underground, potentially for years. Further, those older engines almost always have a carburetor, rather than fuel injection, so they can be fairly readily adjusted to change the fuel mixture to run on ethanol, which is by far the easiest engine fuel to produce new.

$\endgroup$
9
  • 3
    $\begingroup$ Really you just have to back off the ignition timing. If the gas isn't too awful some computer-controlled cars might even do it automatically for you, or only need a few minor tweaks. And ethanol is definitely not the easiest internal combustion fuel to produce new. Producer gas is what you want. No picky fermentation process. No multiple refining and distilling steps. Just load your cellulose scrap in the top and the charcoal from the previous run in the bottom and let it warm up for a bit and off you go. Here's someone with a vintage setup: youtube.com/watch?v=MXaoQ0k9Jlg $\endgroup$ – Perkins Feb 20 at 8:01
  • 1
    $\begingroup$ Ethanol, on the other hand, can be used in minimally modified existing (old) vehicles, or new enough ones to be "flex-fuel" (they claim an E85 limit, but most will run with higher ethanol percentage). "Easiest" includes end use as well as actual production. Retard the timing in a high compression engine to counter knock and the engine will be prone to overheating -- I've seen it happen fifty years ago, when gas still had lead in it, when an engine that needed premium was "tuned" to run on regular. $\endgroup$ – Zeiss Ikon Feb 20 at 14:24
  • 1
    $\begingroup$ Most modern aircraft engines will probably run on additive-free gasoline for a couple of minutes until their fuel pumps seize due to lack of lubrication their usual fuel—kerosene—provides. Most aviation engines that still use gasoline will, however, not run on additive-free gasoline as they are designed for octane number 100 and don't have any controller that could adjust timing to prevent knocking. $\endgroup$ – Jan Hudec Feb 20 at 20:53
  • $\begingroup$ I had a drum of gasoline from 1973-ish. In 2012 (fuel was 40 years old), I tipped it through a particulate filter (really just multiple layers of fine cloth), then ran my 1986 Ford Sierra V6 on it. No problems at all. $\endgroup$ – PcMan Feb 21 at 19:55
  • $\begingroup$ @JanHudec That depends very much on the engine. Many are "autogas" rated, meaning, they'll run on 87 octane regular, and a lot of those in older airplanes (1970s vintage and before, at least, probably some into the 1980s) only call for 80 octane. And it seems disingenuous to bring turbines into this, since the original question was specific to gasoline. $\endgroup$ – Zeiss Ikon Feb 22 at 12:09
10
$\begingroup$

Option 1. Use kerosene vehicles, it has the longest shelf life of petroleum fuels and like all fuels can be pushed further with stabilizers and sealed containers. But even better old diesel fuel and motor oil can be refined into kerosene.

Option 2. Use diesel, diesel lasts a lot longer than gasoline and is far more plentiful than kerosene (in the US at least), plus if you do find kerosene, you can cut it with diesel and the engine will burn the mix just fine.

Option 3. Use a variable fuel steam engine, bulkier than a normal engine but you can burn almost anything in it, from fuel oil to ethanol. Or choose a solid fuel steam engine and burn coal or wood chips. As a bonus, both can be used to make potable water; always a bonus for the survivor.

$\endgroup$
5
  • 1
    $\begingroup$ +1. I recently (2021) filled my VW Jetta TDI diesel with 15 gallons of diesel fuel that I saved in a sealed drum from 2014. It's absolutely fine, runs great. $\endgroup$ – MTA Feb 19 at 16:00
  • $\begingroup$ do be aware ethanol diesel blends have a much shorter shelf life. ethanol is a wonderful fuel but has an abysmal shelf life. $\endgroup$ – John Feb 19 at 16:40
  • 1
    $\begingroup$ As far as I can tell, that flurry of research on ethanol-diesel blending went nowhere, so there is no ethanol-diesel sold in North America today. If ethanol-diesel is sold in any U.S. state today, I'd like to know so I can avoid that state! $\endgroup$ – MTA Feb 19 at 17:54
  • $\begingroup$ @MTA I know it is used in some private and specialized setting, I agree I don't think it is sold at any normal stations. $\endgroup$ – John Feb 19 at 18:45
  • $\begingroup$ @MTA: I've seen something like it here in California. Don't worry, you won't be putting it in your diesel truck by accident. They only sell it to people running steam engines. $\endgroup$ – Joshua Feb 19 at 19:09
5
$\begingroup$

Most plausible future liquid fuels will keep long term in sealed containers.

If your zombie apocalypse hits today - fuel stabilizers / reprocessing as already answered, however if it arrives in the near future, and the country it arrives in is phasing out fossil fuels, you may not need to worry about this.

There are potentially net-zero-carbon fuels that many latest gen petrol cars can already run on (or be modified easily to run on) including things like methanol and ethanol. These can be generated renewably from as little as water, co2, and energy, and if that energy is renewable you have a green fuel that's backwards compatible with existing car fleets.

If this fuel is available like current gasoline it will last a very long time in sealed containers. A sealed underground tank full of ethanol at a petrol station should last until the tank fractures. The fuel will marginally decay when exposed to air (it will absorb water from 100% until 95% ethanol), but there should be no problem sucking underground fuel tanks dry for years if they're airtight.

$\endgroup$
4
  • 1
    $\begingroup$ ethanol fuel actually has a really short shelf life, it oxidizes when exposed to oxygen. even pure ethanol only has a shelf life of a few years if not sealed for the same reason. $\endgroup$ – John Feb 19 at 5:56
  • $\begingroup$ @ John yes must be kept in sealed containers $\endgroup$ – Ash Feb 19 at 6:06
  • 1
    $\begingroup$ keep in mind most fuel containers are not sealable on purpose. underground fuel storage will not be sealed. $\endgroup$ – John Feb 19 at 6:12
  • $\begingroup$ It's much easier to make ethanol than it is to make gasoline in a zombie apocalypse world. We already have Flex-Fuel vehicles that support E85 (85% ethanol) and in Brazil you may find some E95 vehicles. You just need to find the right combination of chemicals for the last 5-15%. $\endgroup$ – rtaft Feb 19 at 16:35
4
$\begingroup$

CNG and propane

There are vehicles that run on methane and propane and they are pretty common. I know the Schwans trucks run on propane, as do many city buses. It's pretty easy to find too in a apocalyptic world. You just head out into the country, almost everyone in rural areas has a tank up north where its usually cheaper to heat with than electricity.

$\endgroup$
1
  • $\begingroup$ Propane has a basically infinite shelf life as well. Container failure is the only thing you have to worry about. $\endgroup$ – John Feb 19 at 18:46
3
$\begingroup$

Ethanol is the main reason gas "goes bad". But the gas is not really bad. Ethanol gradually takes humidity from the air. In normal use, that's not a problem. But left over time, sufficient water is absorbed from the air to collect at the bottom of the gas tank. Gas and water don't mix, not for long.

So the solution I have seen used is to simply let them separate in a clear container (so water content can be seen), and then pour off the pure gasoline into another container. (BTW, the ethanol stays with the water).

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.