Thanks for all your input from all of you.
Maybe I should clarify myself why I need the jerrycan. I have this fear about standing in the middle of nowhere without fuel. I know it's completely nonsense (more so when you only travel in Europe for now) but still...I think it's some kind of fear just like somebody with claustrophobia, who doesn't like small spaces, it makes no sense but it's very real to them. And I have a bike with a small range of 150 miles/240 km so that doesn't make it easier.
Last year I had a lot of stress because of this. But I don't wanna give up traveling on two wheels because I really love it.
So for this year I wanna take this jerrycan with me filled with 5L of fuel, perhaps/probably never use it. Only reason (but a very good one to me) is to feel good and keep the stress to a minimum.

How long can you keep the fuel in the plastic jerrycan and still use it? A week? A month? Longer?

Sounds then like you need a proper & permanent jerrycan! :cool4:

I'm quite sure that fuel in a plastic jerrycan remains good for many months. Just like a plastic fuel tank, one would think. But to play it safe, every so often at a fuel stop why not just dump your jerrycan fuel in the tank and fill the jerrican with fresh fuel. Happy jerrycanning!

I may be a bit late to the party, but ...

1. I have a couple of 20l jerrycans for domestic use (filling mowers etc). These get filled to the brim (noting the designed-in airspace as mentioned above) and thrown in the back of the car on their sides in hot and cold weather. I have never had a leak from either, and not even a smell of fuel if I am careful filling them. So yes, a good jerrycan will make a perfect seal. Mine are about 10 years old, from a Land Rover supplier, and have never had new seals.

2. Hein Gericke sell a neat 2l aux fuel container, made of black plastic. Under 10GBP when I got mine. It doesn't seal perfectly so you have to keep it upright. Also, the neck is too narrow for a standard fuel nozzle, so you need to carry a small funnel as well. Not a perfect product, but a useful addition if you are expecting 'fuel panic'.

In the UK you have to fill these things out of sight of the cashier. If they are following the law, they must stop you filling them. But I have only been told once in twenty years :) As others have said, I would not like to risk petrol in a Coke bottle, but I have heard of people doing it without problems.

You should fill whatever container you select to the very brim - that way there is no space for vapours to build up within the container. Half empty containers swell to quite alarming propostions when shaken about and left in the sun.

On my last trip stopping to have a smoke and venting off the built up petrol vapours from a 5l jerry can was a regular chore. Possibly not the wisest combination of activities and proof that someone is always that stupid!

One should think that because there is no space for vapors to build up it might blow!

Not true. Vapour expands proportionally far more than liquid. There will be a slight expansion of liquid fuel in the heat, but fuel vapour will expand a lot. If there is no room for the fuel to vaporise, it will remain liquid (all other things being equal).

The original designers of the jerry can understood that there needs to be a small airspace to allow for fuel expansion, but not enough to create a huge volume of fuel vapour. Good article here.

It's the half-empty ones that give you a nasty surprise on a hot day, not the full ones!

Well, that is sure is a good tip then, thank you! Normally I would have filled it up to 80 percent, now I will fill it up completely!

Must have Jerrycan
 

Here in the US we have :
STA-BIL® Fuel Stabilizer will keep fuel for up to 12 months http://www.goldeagle.com/brands/stabil /default.aspx

I'm sure you have the same thing there may be under another name but if you can't find something, Amazon has it.

I have a Mini Moke that only has around 300km range and a non-functioning fuel gauge. So I run out every now and again. doh

I'll soon be adding an extra 20lt tank to extend the range and I will have a working fuel guage for each tank.

Meanwhile I keep a 5lt can in the luggage compartment on one side in case I run out. If there is any in the can I tip that in the tank first before I fill the tank and the can. That way the fuel in the can is always fresh. I've never had the can leak.

Unleaded fuel lasts about 6-8 weeks in storage before it starts to go "off".

Cheers,
Brett.

OK, I didn't know that existed! But my plan is to keep the fuel in the jerrycan for a couple of days or a week. Then I will fill up the bike with the jerrycan and refill the jerrycan (a bit like Brett said). So I don't think I need to use these cans. But it's nice to know it's there.

Filling to the brim?
 

Filling jerrycans, or any tank for that matter, to the brim is not the right practice. Fuel is a liquid and thus cannot be compressed, which is why we use brake fluid to operate the brakes for example. When fuel warms up it will expand, the air above the fuel allows the fuel to expand as air can be compressed. Filling it up to the brim with cold fuel, which then expands as it warms up, creates an hydraulic pressure way beyond the capabilities of the jerrycan. It will burst or blow the cap or whatever is the weakest link! No question about it
The manufacturer doesn't put that maximum fill line on for nothing.

Agreed, except that jerry cans (and I mean the proper thing, not a generic term for fuel can) have the necessary airspace designed into the top of the can. Holding the can level, you cannot fill that space with fuel as it is above the filler neck. Therefore, there is no maximum fill line (at least, none of mine has one).

If you design something for use by squaddies, it has to be foolproof! (No offence intended to any squaddies reading this - I mean in battle conditions things like fill lines get ignored.)