There's nothing wrong with it being in a sealed bottle IF you keep it out of direct heat, or in a climate controlled environment. Coleman sells both kerosene and "white gas" in sealed plastic bottles which can easily be found at sporting good stores or walmarts. White gas is basically gasoline without additives and lower octane, around 50-60 octane i believe, so technically more flammable. If you are going to store these in a garage or shed that has temperature swings, you'd be advised to leave the cap cracked open till the garage/shed reaches is typical max temp during the day, then seal it. When it cools the bottle will collapse as the gas shrinks, but then it has expansion space when it warms up the next day.