Jelly - you should try the library and check out some handbooks. I tried looking online and couldn't find the info. Internet is great but sometimes the hard copy stuff is so much easier. My 63 yo brain can't recall for sure but you could look up some of this is a CRC Chemical handbook or better yet, I think it is Sax's Handbook of Dangerous Industrial Materials...(or something like that?) May be out of print, but it has a good listing of such things as flashpoint, LEL and UEL, vapor pressures, as well as a good description of how to interpret. Using gasoline in a lighter would be downright dangerous as others have said.... You are obviously an inquisitive person, but be careful of making generalizations as naptha and gasoline are in same family. A little knowledge can indeed be dangerous. Gasoline is dangerous material, but because we have been using it so much in our daily lives it doesn't get the respect it deserves, safety wise. I'll get off my soapbox now....