Kill two birds with one stone by selling it off to some boy racers. Fuel gone and boy racers with dead engines :)

There are fuel conditioning services where a man in van comes around and adds additives and cycles & filters fuel that has sat for a long period of time - I've seen this done for large diesel generators with 1000's of liters of stored fuel.

Fuel goes stale because lighter components evaporate. Because it is the lighter components that evaporate, stale fuel has a higher octane rating than fresh fuel.  There's also an oxidation reaction that happens, and can happen in the absence of air. As it happens, the fuel changes colour to a darker, greenish hue and becomes more viscous. Storage temperature is very important -- below 20C petrol is OK for 6 months or more, above 30C and it's down to a few weeks. If you can see or smell a difference, I'd save it for Guy Fawkes and have a really good bonfire.

If it's in a full sealed container then none can evaporate and there's limited oxidation, so it should be OK, especially if it has been kept cool. If it's in a sealed container with some air then a good mixup will redissolve all those evaporated parts, but won't undo any oxidation.

If it smelt and looked OK, I'd probably mix it into some fresh fuel in the car, say 50-75% fresh. 

Perhaps add some fuel stabilizer in.
It may be too late , but might help ?

Note the mention of sticky resins forming in stale fuel , in the link below
https://www.berrymanproducts.com/fuel-stabilizer/

cokemaster:

 

@Rikkitic - on a more serious note... you could probably won't want to use any suspected stale in anything modern.
With older equipment, you could probably blend it in with fresh fuel and burn it off slowly that way. I do that with my lawn mowers. 

 

This ^^^

I've a side-hustle buying/selling heavy equipment & machinery.
Last summer I got a call from a low loader driver - onsite doing an excavator pick up - complaining that they were trying to make him load hazardous/flammable goods.

I called the Auctioneers, they pointed out that the bid-sheet clearly stated an 'and an unknown quantity of waste fuel in drums' - no wonder I'd won that lot with a lowball bid...
My haul included two dozen 205 litre drums of expired jet fuel, diesel and ethanol blended gasoline. I'd missed reading that bit and was obliged to remove it from the site.

I literally broke out in a cold sweat wondering how much disposal would cost and thinking I was about to lose my shirt on this deal.

The good news- not all the drums were full.

Then we ran all the diesel and Jet-A through filters, removed the gelled lumps and water, blended it, and it's been running irrigation pumps and a couple of older GM pickups just fine.
We'll use the final 700l up this year, and the farmer who took it actually spotted me some money - which almost covered my cost of collecting it from 300km away.
Turns out diesel's nearly indestructible.

The gasoline (though mostly yellowish and with a kerosine-y smell), after filtering, we've been blending 50/50 with fresh (dyed) farm fuel.
It's been used in ride-on mowers, older (1990s - 2010's) pickup trucks, cars, carbureted tractors and a hay-rake. Some of it was more than 8 years old if the labels on the drums are to be believed.
It likely had stabilizer added, and I wouldn't use it any modern (valuable) vehicle, the ecu's fuel injection systems and catalytic converters might not be happy.

Careful with the Jet-A in diesels - it lacks the lubricity of diesel fuel so can be hard on the injectors and high pressure pump.

I have used some very old stuff in my mower and generator with no problems at all. If its mixed up 2 stroke, then forget it, but straight 95 stored in a sealed plastic can seems to last very well.

Many horror stories of it going off are from the US where fuel is in general terrible quality, with lower quality stuff boosted up with butane and other really light stuff in the mix that evaporates very fast leaving the thicker stuff behind. Also ethanol is a problem there. NZ fuel (at least for now) is pretty good quality.

I have had some go pretty bad in the generator where it was a vented tank. That shed always smelt of fuel too, so it would have been evaporating all the good stuff. It ran really badly till I topped it up with some 95 or 98 and was then good.

johno1234:

 

Careful with the Jet-A in diesels - it lacks the lubricity of diesel fuel so can be hard on the injectors and high pressure pump.

Mehrts:

 

johno1234:

 

Careful with the Jet-A in diesels - it lacks the lubricity of diesel fuel so can be hard on the injectors and high pressure pump.

It's fine if mixed in with diesel or some other light oil which helps out with the lube. I'd also only run it on older diesel engines. Common-rail engines won't like it very much!

 

We mixed roughly 8 drums of the very stale diesel with 6 of the kero. Plus whtever diesel was left in the feed tanks we pumped it into.

The old (>50K hour) JD 6404's -  there's probably not a factory tolerance left in 'em - happily drank over 2000 litres of that goop last summer.
Those rotary Roosa-Master's could probably pump concrete dust anyway. Lol. Same with the IDI 6.5's in the bale-trucks.

More worrying was the old (yellowish) gasoline mixed 50/50 with (red) farm gas which gave us ~2400l of an orange-ish 'witches brew' type substance.
Their early 00's Dodge farm truck's injectors haven't clogged up - yet. They're not exactly high-value items, so if they do they'll likely just push them into a hole.