I try and keep the petrol tank in my car reasonably full. But I also have a 10 litre can of petrol stored in the boot (trunk) for emergencies. I try to exchange it every few months. Am I being over-zealous? Could I leave it there for a year or so?
Are you using fuel stabilizer here or not?
No - just straight from the pump.
I wouldn’t go a year. A car will run on year old gas but it won’t run well.
Every few months is good and I wouldn’t call it being over zealous.
And even if it is, it isn’t costing anything except a few extra minutes. Modern gas is pretty stable by design, and a year probably isn’t pushing it too much, but there’s certainly no harm in changing it every few months and if you’ve gotta get it started after running the tank dry, fresh gas is a better bet than old.
Dang! With all the crazy drivers on the roads around here that rear-end others, I sure wouldn’t keep a can of gas in the trunk. Just too dangerous for me!
And why? Can’t you just keep an eye on the gas gauge, and pull into a filling station when it gets close to empty?
Where in the hell are you going to get stranded in the UK where you’d need 10 liters of gas/petrol for an emergency?
I’d just use something like Sta-bil or whatever the UK equivalent is- it’s supposed to make your gas useable and gum-free for up to a year, according to the bottle.
From a fire standpoint, this isn’t a good idea. The primary fuel tank has the benefit of engineering to locate and secure it in a manner that’s not likely to increase the peril of fire during a crash. Gasoline vapor is also appropriately managed as part of the emission control system. The same can’t be said of a spare can in your trunk.
The advice I heard was to keep an empty petrol can in the boot, both for fire safety as mentioned, and also to reduce the weight by the fifteen pounds that ten liters of petrol weighs.
This. Rear-end collision, boom! I’ve been driving almost 30 years in the US and have never had extra gasoline in the trunk. Is this SOP in other parts of the world?
I could see it maybe if the can is outside the vehicle, like on the back of an SUV…but inside the trunk (boot) it sounds like a science experiment—perfect mixture of fuel to air—waiting to happen.
Lots of places, actually. Besides, it might not be myself that’s run out of petrol.
The can is airtight and doubly locked (clamp and cotter pin), and it’s solid metal and military-standard. It’s actually stronger than the car’s petrol tank. It’s not one of those plastic petrol cans people have for refilling mowers.
A slightly different question if I may. Is there a difference in storage life between straight petrol and petrol/ethanol blends?
How often do you run out of gas?
I’m not the OP, but twice now I’ve run out of gas on the road. My car’s gauge doesn’t work, so I have to go by the trip meter and fill up once it reaches 300 miles. Theoretically I can get 400 miles or so out of it, but I try not to push it past 350. There’s been a couple of times where my mileage was so poor that I ran out of gas before 350 and it died on the road.
Obviously I don’t let it get anywhere near there before filling up these days, but a spare fuel can in the trunk would have been extremely helpful.
Mebbe it’s me, but rather than expose myself to the risk of fire, I’d just fix the gauge. 
I’ve always had a can of petrol in the boot of the car, ever since I started driving, nearly 25 years ago.
I sincerely wish you continued good luck. However, I stand by my earlier post, based upon the 35 years I’ve spent in the fire service. IMO safety trumps convenience.
10 Litres is about 2.64 Gallons of gas. Here is a video of 3 gallons of regularly available U.S. gas blowing up (they put in firework rockets to make a cool effect) but you can see why people would be concerned for you in the event of an accident.
Yeah our “Nanny State” has been trying to spoon feed us that principal for a few years. Forgive a little rebellion
Personally, I would say paying for membership with AA or RAC would be cheaper and more useful that carrying around fuel and changing it three or four times per year.
10 Litres would cost at least £12.50 at current prices. Three of those per year and you’ve paid for your road-side support membership.
And they’ll fix more than lack-of-fuel.
This would assume that when changing out the fuel, you’re pouring it down a drain. If the OP is really hell-bent on keeping extra fuel in the trunk, the thing to do would be to pour it into the car’s tank and then top off the spare can every month or two.