As has beenn commented on, the rubber seals perish if not fuel rated causing leaks.
IMHO, stick with a dedicated fuel bottle - safer, clearly marked etc.
Simon
Luck of the draw mate, I've had fairly expensive ones not work with various fuel types
eg meths, paraffin, coleman fuel. i bought some cheap ones from a pound shop that worked well. So if you find one really cheap might be worth a go. Try putting your fuel of choice in it ( small ammount) and lie it on its side/inverted somewhere a leak wont matter to test it.For a week or two then examine the state of the seal.
Just dont use it somewhere mission critical straight off. All the above stink and can damage all kinds of other gear if they come in contact with it in your pack or wherever! Don't taste too good in your rations either!
You can sometimes cut cost by using a cheap bottle and discarding the top (especially if its a sports type) and replace with a proper spare top from a sigg or similar as they sell them separate sometimes and they come with their own seal. You can try and see if the thread is compatible as many are straight rip offs if a mate has a sigg (or the shop sells both)
