If you’ve left fuel sitting in a vehicle, jerry can or storage container for several months, you may be wondering whether it eventually goes off.
The short answer is yes. Both petrol and diesel have a limited shelf life, although they deteriorate at different rates. Old fuel can reduce engine performance, make starting your vehicle more difficult and, in some cases, damage parts of the fuel system.
Here’s everything you need to know about how long petrol and diesel last, how to tell if fuel has expired, and how to store it safely.
If you’re thinking about replacing an older vehicle that has been sitting unused, take a look at our maintenance guidance hub for more expert guides on maintaining, buying and selling your car.
How long does fuel last before it expires?
Petrol generally has a shorter shelf life than diesel, while fuels containing ethanol tend to deteriorate more quickly than standard unleaded petrol.
Typical shelf life under suitable storage conditions:
Petrol
- Around 3–6 months in a sealed container stored in cool conditions.
- Around 1–3 months in warmer temperatures.
Diesel
- Typically 6–12 months when stored correctly.
- May deteriorate sooner if exposed to moisture or contamination.
Although fuel doesn’t suddenly become unusable overnight, it gradually loses its effectiveness as it ages.
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Can expired fuel damage your vehicle?
Yes.
Using old or contaminated fuel can cause several problems, including:
- Difficulty starting the engine.
- Reduced fuel economy.
- Rough running or hesitation.
- Blocked fuel filters.
- Deposits forming within the fuel system.
- Corrosion caused by moisture contamination.
Over time, degraded fuel may leave varnish-like deposits inside the fuel system, particularly if a vehicle has been left unused for extended periods.
If you know fuel has been sitting for many months, it’s often best to replace it before driving regularly.
How can you tell if fuel has gone off?
There are several signs that fuel has deteriorated.
Old petrol or diesel may:
- Appear darker than fresh fuel.
- Look cloudy or contaminated.
- Develop sediment or particles.
- Have a sour or stale smell.
If fuel looks significantly different from fresh fuel or smells unusual, it’s usually safer not to use it.
If your vehicle has been standing for a while and you’re thinking of selling it, our guide on Can I Sell a Salvaged Vehicle? explains what to expect and how to maximise its value.
Is it legal to store fuel at home?
Yes, but there are rules you must follow.
In the UK:
- You can store up to 30 litres of petrol at home without notifying your local Petroleum Enforcement Authority, provided it is stored in suitable containers.
- Diesel does not have the same specific domestic storage limits, although it should still be stored safely.
Fuel should always be stored:
- In approved containers.
- Away from direct sunlight.
- In a cool, well-ventilated area.
- Away from naked flames or other ignition sources.
- Out of reach of children.
If you intend to store larger quantities of petrol, additional legal requirements may apply.
What container should you use to store fuel?
Fuel should only be stored in containers specifically designed for petrol or diesel.
Suitable containers include:
- Approved metal fuel cans.
- High-density polyethylene (HDPE) fuel containers.
- Certified jerry cans.
Always ensure the container is:
- Properly sealed.
- Clearly labelled.
- Stored upright.
- Kept away from heat and direct sunlight.
Using unsuitable containers can increase the risk of leaks, contamination and fire.
Can you make fuel last longer?
If you’re storing fuel for an extended period, a fuel stabiliser may help extend its usable life.
To maximise shelf life:
- Store fuel in sealed containers.
- Keep containers cool and dry.
- Avoid exposing fuel to air or moisture.
- Rotate stored fuel regularly.
Vehicles that sit unused for long periods may also benefit from occasional engine starts or fresh fuel being added before use.
Does premium fuel last longer?
Premium petrol doesn’t necessarily last longer than standard unleaded.
While premium fuels often contain additional detergents and additives, they are still susceptible to oxidation and degradation over time.
Proper storage remains the biggest factor in extending fuel life.
Final thoughts
Although petrol and diesel don’t expire overnight, they do gradually deteriorate.
Fresh fuel helps your engine perform efficiently, while old fuel can lead to poor starting, reduced performance and potentially expensive repairs if left untreated.
If you’re storing fuel at home or leaving a vehicle unused for several months, following safe storage practices can help reduce the risk of fuel degradation.
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