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Refined essence of prehistoric ooze used to be a waste by-product. Now, everybody needs it.

What was gasoline good for before there were cars?

The short answer: nearly nothing. This wasn’t exactly a case of build it and they will come, but oil companies produced gasoline before anyone had a use for it. They really had no choice—gasoline, or a semblance of it, was a by-product of kerosene, their main product after the world’s first oil well struck liquid gold in 1859. Gasoline was essentially a waste product.

The situation began to turn around in the 1890s with the birth of the auto industry. Even the relatively unsophisticated engines of a century ago wouldn’t run well, or at all, on kerosene.The car and gasoline grew up together; in 1911, gas sales zoomed past kerosene.

What’s in it?

Chemistry can be a yawner so, to be brief: Gasoline is made from crude oil, which is a mix of chemical compounds—hydrocarbons—formed from hydrogen and carbon with a few other elements included in small amounts.

While the basic chemicals are probably as old as the earth, it’s generally accepted that they had to go through an organic stage before becoming oil. Some of this happened during the age of dinosaurs, but it’s unlikely many actual dinosaurs got involved. It appears that oil’s organic stage was mostly of the single-cell variety. The prehistoric world evidently was a slime-rich environment.

What else is in it?
These days, gas is a mixture of hydrocarbons with many additives. The extra ingredients perform a variety of tasks. Additives include octane enhancers (to prevent knocking), detergents (to prevent crud deposits on, for example, fuel injectors), and corrosion inhibitors (to prevent rust).

Two additives in particular, lead and MTBE, have proven controversial. No longer used in domestic gas, lead is the granddaddy of additives, first used in the 1920s to improve gasoline’s antiknock properties. It was phased out in part because it destroys the catalytic converter required by the federal government to reduce car-caused air pollution.

More recently, MTBE was used in small amounts for the same purpose as lead. Currently, it’s used in many areas to reduce exhaust emissions. MTBE use has become controversial: A Univer- sity of California study finds that it causes cancer in animals. The study maintains that advanced auto technology diminishes its value in reducing air pollution. The extent of any health threat it may pose and even its value in reducing air pollution both are topics of heated discussion.

What’s the right gas for your car?

All the major gasoline producers include additives with their gasolines. The ingredients are not uniform from refiner to refiner, but the end results generally are the same. Refiners do measure the antiknock properties of their gasolines in a uniform way, with an octane number, typically ranging from 87 (regular gas) to 92 or so (premium). Often there’s an intermediate grade, too. When you’re choosing from among major brands, gasoline can safely be bought on the basis of price and octane rating.

Your car’s owner manual tells you the car’s octane requirement. Most cars use regular. You do the oil company a favor when you use premium in a car designed for regular. You don’t do the car a favor; it won’t even detect the difference, let alone credit you with having made a nice gesture. You don’t do yourself a favor, either, as fuel economy is unlikely to improve.

Occasional, light knocking probably doesn’t harm an engine. However, if your car pings or knocks more than occasionally and lightly while using gas of the correct octane rating, try the next grade up or try another brand of gasoline. If that doesn’t do the trick, the knocking may be due to mechanical problems with the engine, and a trip to the shop is probably a good idea.

This article was first published in May 1999. Some facts may have aged gracelessly. Please call ahead to verify information.