Random Facts About … Gasoline, Octane, and Ethanol


By David Martin – 

This gas crisis is affecting everything. When we opened our internet tubes this week, nothing emerged because … wait for it … our search engine was out of gas.

When the first wells began producing crude oil in the 1860s, that oil was distilled to produce kerosene. One byproduct of the distillation process was gasoline, which people didn’t have a use for and was often discarded. The growth of the auto industry and the switch of fuels from kerosene to gasoline meant that the oil industry concentrated on producing gasoline. Today, about half a barrel of crude oil goes to making gasoline while the other half produces diesel, home heating oil, jet fuel, kerosene, and everything from cosmetics to toothpaste to contact lenses.

An internal combustion engine running on gasoline produces its power when a spark plug ignites the gasoline- air mixture at exactly the right time, causing an explosion that pushes down a piston that turns a crankshaft that makes the wheels go. But if there’s enough pressure in the engine, the gas can ignite from heat before the spark plug fires and this messes up everything. You can hear when this happens because the engine knocks. As car engines became more powerful with higher compression and more heat, the knocking became more of an issue.

To reduce knocking in high-compression performance engines, gasoline is formulated with higher octane, which means that the gas resists igniting from heat and pressure. The higher the octane, the more the gasoline resists igniting prematurely. Octane is increased by adding various ingredients, but the most efficient and cost-effective was tetraethyl lead, creating leaded gasoline. Old-timers might remember some hotshot coming into a gas station with a high-performance car and telling the attendant, “Fill her up with ethyl.”

Lead was bad for people who had to deal with it and bad for the environment. Leaded gas was phased out and finally banned in the U.S. in 1996. Refineries used other petroleum products to boost octane.

Ethanol, which is basically highproof grain alcohol, will also boost octane and is cleaner and better for the environment than lead was. Gas with 10% ethanol is generally available everywhere in the U.S. Potential negative effects of ethanol in gasoline is damage to engines that haven’t been designed to run on gas-with-ethanol and diversion of a food source (corn) from feeding people (and the animals that feed people) to fuel. But because it’s friendlier to the environment, is an income source for farmers, and saves oil companies money (ethanol added to low-quality gasoline can boost octane to acceptable levels), ethanol seems here it stay.

If the manufacturer of your car’s engine says it requires a certain octane and you feed the beast lower octane and especially if knocking occurs, you could be causing long-term damage. On the other hand, if you use gasoline with a higher octane than the engine calls for, you’re not doing any harm but you’re not helping the engine. Technically, higher octane gasoline has less energy than lower octane gas, and using higher-than-necessary octane won’t improve your car’s performance.

Don’t buy high-octane, high-price gas if your car doesn’t call for it and maybe you won’t have to take out a second mortgage to fill your tank.

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