Nope, not really a big fan of "Wiki" but it does have some interesting data on barrels, and the sizes and volumes of barrels over time. (Appears the shipping world has been anal for centuries about weights and volumes, even without computers, you still have a world run by bean counters... LOL)
42 usg. is a "barrel" of crude oil.
When cracked/seperated by heating it into gas, diesel and other stuff, it grows in volume somewhat, kinda like pop corn...
I can't belive the crap attached to a search on this topic. Sites for kids written by eco terrorists... No wonder everyone is screwed up by the time they get out of high school. (Myself included... LOL) We are teaching our kids outdated theory, and outright lies in some cases, and it's these eco-friendly zelot's who are funding and running the sites. (Like Wikipedia for example.)