Any watch the History Channel? Oh i love that channel.

yesterday (jan 26) they have a show called Modern Marvels. On yesterdays episode, they explained how they make gas. It is very interesting, i cant explain it all, but the basics of it. They get the crude oil and boil it at around 700*F., from bottom to top here is what is made out of boiling it. tar, thick oil (the kind you put in your car), thinner oil,gas (the kind we use) then gases that ecscape from the top. 3/4 of the way up is an outlet so the gas can drain out. In a normal barrel of crude oil,50% of it is acually made into gas.

When you go to the gas station you see 87 89 or 91 (depending on state) that means 87,89, or 91 percent octane, and 13,11, or 9 percent heptane. Octane is the anti-knock property and is stable at a moleculare structure. Heptane is very unstable (pre-ignites real easy) but burns cleaner. Back in the day they used lead to improve the anti-knock, but due to regulations on air quality, it was stopped a while ago. So, when you go to get gas, get the cheapest one and if it knocks, go to the right gas or what is recommended by the manufacturer.
So, if anyone always wondered about gas like i did everytime i went to fill up, here is a breif discription on it. Also check this out on how and why gas prices go up and how we are affected.
Info on gas price fluxuation

enjoy
kevan