Gasoline has a shelf life, and it’s much shorter than you might think

The gasoline in your car began life (for lack of a better term) some 360 ​​million years ago. This was long before even the first dinosaurs roamed the earth; Despite the concept car’s popular image it’s fueled by the explosion t rexisIt’s actually ancient algae and plankton. Considering how long it’s been hanging around so far, it seems especially unlucky to us that we got it so close to its expiration date.

How long does it take for gasoline to expire?

That’s right: while post-apocalyptic visions of the future such as The last of us or Mad Max Everything seems to happen in worlds where years-or even decades-old gas is usable and valuable, and the reality likely involves less “jumping in an abandoned Chevy and doing a quick getaway” and more “vainly trying to start the engine while sniffing.” One of the most disgusting smells I’ve ever smelled.”

“Gas Do It has a shelf life,” Matt Crisara confirmed in a recent article for Popular Mechanics. “Left dormant in your car’s tank, it can expire in as little as four weeks.”

With proper storage, this can be extended somewhat: “You can expect anywhere from three to six months with fuel that has been stored in cans – in proper conditions,” Crisara explained, while “fuel stabilizers can enhance the shelf life of Anywhere between one to three years in the best of circumstances.”

Why does gasoline spoil?

To understand the different ways your fuel can go bad, we first need to look at what gasoline actually is He is – This is no simple task.

The stuff you’re pumping into your car’s gas tank is a very different substance than the crude oil that was pumped out of the ground hundreds of millions of years after this algae originally died. Certainly, in its simplest description, it is the same: it is a mixture of hydrocarbons of different weights, which can be burned to provide energy.

However, between that and the gas station, it goes through some significant changes. The heavier hydrocarbons are ejected, leaving the fuel as a mixture of paraffins (alkanes), olefins (alkenes), and cycloalkanes (naphthenes); Impurities such as sulfur are removed in the refining process; Substances such as ethanol, anti-rust agents and other things designed to improve vehicle performance are added.

It’s some of these additives that can cause one type of problem with residual gas. Ethanol, for starters: It’s put in the mix thanks High octane numberas well as its supposed ability to slight Reducing the carbon footprint of your car that consumes fossil fuels. However, they are also hydrophilic – they like to bond with water – and this can cause major problems for your car.

“If there is ethanol in your gasoline, it may start to absorb water vapor from the air and put it into the gasoline,” said chemical engineer Richard Stanley. live science. “You don’t want water in your engine, because it starts to corrode the system.”

Then there are the olefins. Because hydrocarbons have a double bond between two carbon atoms, these molecules are especially vulnerable to a process called oxidation — they start reacting with oxygen in the air, creating a hard, gum-like substance that can mar your engine.

“Once [the bad gasoline] Gets into the pipeline, that gum may break off […] And maybe [it will] Don’t completely block the gas line, but it might [it will] James Speight, an independent fuel and environment consultant and author of more than 100 books and papers on oil refining and processing, told Live Science.

“You could almost say that soiling gas lines is like hardening of the arteries,” he added, likening your car pickup to the buildup of cholesterol deposits in the body’s arteries.

This is not the only way that gasoline spoils. Since the fuel consists only of the lightest hydrocarbons of crude oil—which generally consists entirely of those chains with 12 carbon atoms or less—leaving it out for too long can actually cause some of those molecules to evaporate away. This can be especially problematic if you’re trying to run your car in the summer with the gas that’s been in the tank since winter, Speight advised: Petroleum companies change the mixture of hydrocarbons in petrol from season to season, so as to better deal with heat or cold temperatures – and winter fuel is more likely to evaporate than its summer equivalent.

“If you leave the gasoline alone, over time […] “It just doesn’t perform the way you think it would,” Stanley told Live Science.

Gasoline, he said, is “like wine. Once you take it out of the bottle, it starts to spoil.”

What do you do if your petrol is expired?

So she decides to go for a drive, only to encounter a tank full of muddy orange mud that smells like—in Crisara’s words—”an old gym sock that’s been soaked in milk and left to rot for years.” What do you do?

According to British car service company The RAC, it depends on how full your fuel tank is. “If your tank is full of old fuel (especially old diesel), have it drained by a garage or by a professional mobile service,” They advise.

If you’re working on a little less, you may have a cheaper option. If you are in doubt about your gasoline [aka gasoline] or stale diesel, the best advice is to try fresh fuel from a filling station.”

Of course, the better tactic is to store the gas in such a way as to increase its shelf life. “The main enemies of fuel storage are oxygen, water and heat,” William Northrup, a professor of mechanical engineering at the University of Minnesota, told Popular Mechanics. Reducing the impact of those effects in particular.

To that end, it’s a good idea to store the gas in a fairly full container, Northrop advised: “Some of the volatile components will evaporate,” he explained, “but once the concentration of these volatile components gets high enough in the vapor, they no longer want to evaporate because they create an equilibrium.” between the vapor phase and the liquid concentration.

More important than a full container is the environment around it. Keep any gas you store somewhere with a consistent temperature and low humidity, Northrop advises—and remember: By its very nature, gasoline is truly Not something you want to treat lightly.

“Remember, benzene is very volatile,” Speight told Live Science. “It’s not worth trying to hoard large quantities. It can only lead to trouble.”

He added, “Anything that makes the gasoline more volatile than normal affects the gasoline” – joking that “on a hot day… [that can include] Looking at things the wrong way.