Fuel Degradation

[Marty Funkhouser]

A question for the PH masses here - in the event of an apocalypse, how long before the petrol sitting in the storage tanks in garage forecourts would degrade to the point that it would not "work"?


TIA

[EarlOfHazard]

i'd say less than diesel, so make sure all your internal combustion engines are oil burners.

[red_slr]

A few years before it wont run an engine. After 12 months you will generally get rough running and difficult to start - but once you get it going it should still run. Cars with carbs tend to be worse FWIW.

[red_slr]

Diesel would have the advantage of being able to run on different types of oil.

[King Herald]

Ethanol fuel is bloody awful, absorbs water from the atmosphere and its burny volatile stuff evaporates, eventually leaving a hard, gooey, sticky mess that is impossible to clean off. It would be okay if it were sealed and air tight, like in fuel injection systems, but in a tank open to the air, or in a carbureted engine, it dies pretty quickly.

[mike74]

On a more serious note, just how quickly does fuel degrade? Especially the higher octane stuff, are we talking weeks or months?

[King Herald]

A month, and my four barrel carb was all but ruined, left with fuel in, in high heat area. I had to scrape it clean.

[red_slr]

mike74 said:

On a more serious note, just how quickly does fuel degrade? Especially the higher octane stuff, are we talking weeks or months?

Generally modern fuel in modern cars start to go off after about 4-6 months. It will generally still start and drive as "normal" but it wont be burning as nice. i.e less power. After 12 months you may get issues starting and running rough. A top up with fresh fuel usually sorts it.

[Loyly]

Varnishing is an issue on carbs, as the above poster knows. Bloody ethanol doesn't help. I left my Triumph Daytona sat with a tank full of petrol last winter, a good five months without running it. It started fine and seemed to make good power, I ran that petrol out and refilled it.

A bigger issue is, in half full plastic tanks, the ethanol can cause them to deform! What wretched stuff.

[petop]

From a military point of view, petrol will be submitted for testing after 12 months. 9/10 it will pass but then have a "use within 6 months".
Diesel....ive used ex Russian diesel from the Soviet occupation of Afghanistan in certain equipment and its fine. It all depends how it was stored. Underground tanks, full to brim, steady temps, no water all good. Above ground, water not drained off, half empty and venting all the time then not so good.
Fuel can smell off so this can be a good sign, but only if you know what fuel is meant to smell like. Also just looking at it in a clean glass jar can help.