A Barrel of Oil, Refined

Friends, the "KnowledgeNews racing team," led by drivers Duncan Ende and Grant Maiman, has just one race left in the season, and their brain-stickered car sits in the middle of the standings. So, for the final race, can we spice up their fuel? Make a special, victory-assured blend?

Maybe not. But we can learn how Big Oil makes the gas that powers our cars--how oil refineries turn every 42-gallon (159-liter) barrel of oil into 19.4 gallons (73 liters) of gas, 10.5 gallons (40 liters) of diesel, and 4.1 gallons (16 liters) of jet fuel, not to mention lots of other marketable stuff.

We Want Gas

Gasoline, petrol, benzene--whatever you call it, these days, we prefer our thick black crude as clear car juice. In the United States, for example, about 45 percent of a barrel of oil winds up as gasoline. Back in the 19th century, when horses ran on oats, oil was used mostly as kerosene for lamps. But with more than 240 million "horseless carriages" on U.S. roads alone, those days are in the rearview mirror.

Today, refineries put crude through multiple processes to maximize gasoline production. The chemical energy packed inside all that gas is enormous. If you could digest gas like a car (you can't; don't try), just one gallon would fill your tank with 31,520 Calories! Unfortunately, like your car, you'd excrete more than 5 pounds (2 kg) of carbon after.

Boil Your Oil

So how do you make gas? You boil your oil; you distill it. "Oil" is really a mix of hundreds of different hydrocarbon molecules--carbon atoms bonded with hydrogen atoms in various lengths and structures. Some of the hydrocarbon molecules are small and light. Others are long and heavy. All have different properties.

Fortunately, these hydrocarbon molecules evaporate at different temperatures. So when you gradually turn up the heat, you can capture the various kinds of hydrocarbons one by one. The (relatively light) hydrocarbons for gas boil off fairly quickly. Longer, heavier hydrocarbons--like those used for diesel fuel, heating oil, and lubricating oil--boil off later.

Let's Get Cracking

Still, if you want to meet today's demand for gasoline, distillation isn't enough--you need to get cracking. Simple distillation yields too many long, heavy hydrocarbons. So, to double or even triple the amount of gasoline we get out of a barrel of oil, refineries take these longer, heavier hydrocarbons and crack them apart, making more of the lighter hydrocarbons we use for gas.

Today's refineries can even re-form gasoline hydrocarbons to get more octane--hydrocarbon molecules with eight carbon atoms. Octane handles compression better than other gasoline hydrocarbons. More octane in the mix means smoother combustion for your car.

Next Race: No Gasoline Allowed

When Duncan Ende rides again, we'll look at possible fuels of the future. Already the IndyCar racing series uses 100 percent ethanol fuel in its 650-horsepower V-8s. The future?