Running on Fumes? Why the Octane Matters in Terms of Cost

Some vehicle owners believe higher-octane fuel gives a better performance. Higher octane doesn’t give a better performance, and it’s unnecessary. If, you’re trying to save on fuel costs, you may consider using regular gasoline instead of premium. Regular gasoline gives the same performance at a lower price. So, when trying to save on fuel cost, it pays to use the required octane level for your vehicle.

Vehicle owners have made the mistake of believing that higher octane gives gasoline a better performance. Most engines are designed to take regular unleaded gasoline, which has an octane level of 87. Using higher octane doesn’t improve performance. Actually, octane has nothing to do with the gasoline’s performance, just its volatility factor in the combustion chamber. The higher the octane, the more stable the gas in the combustion chamber environment. Higher-octane fuel is only needed for high performance cars. High performance cars need higher-octane gasoline, because the combustion chamber environment is much hotter. Experts from the Automobile Association of America (AAA) say about five percent of cars sold in the US require premium gasoline. Yet, premium gasoline accounts for 20 percent of all gasoline sold in the US.

If your car does not require higher-octane gas, then you shouldn’t buy it. Sometimes the lower octane may be too low for your car and the mid grade or higher octane may be more than what you need. To avoid overpaying and still get the correct octane for your car, you can mix the gas. For example, if your car takes 87 octane and the pumps have 85 octane and 89 octane, then when filling your car, fill half the tank with 85 octane and the other half with 89 octane and this will give you an equivalent of 87 octane. Check your owner’s manual to see what fuel octane rating your engine needs. Drivers should use the octane level your vehicle’s manufacture recommends. Buying higher-octane fuel is a waste of money. Higher-octane fuel pollutes more, and it costs more. It’s always smarter to follow the manufacturer’s recommendation on the level of octane to use.

People believe buying the “premium” will make their cars run better, but it makes your engine run hotter, and can cause more harm than good. In most of the U.S., regular gas has an octane rating of 87, mid grade is 89, and premium is 91 or 92. Using high-octane fuel reduces pre-ignition in the upper regions of the combustion chamber, which can damage valves, and pistons if allowed to go for long periods of time. Resist buying higher-octane gas for premium performance. It can cause other problems to your engine. Using higher-octane gas, when it’s not required could force some drivers to pay for unnecessary repairs. A “knock” or “ping” occurs when part of the fuel-air mixture in one or more of your car's cylinders ignite spontaneously due to compression, independent of the combustion initiated by the spark plug. If your car runs poorly or “pings” on the grade of gas recommended, it may need servicing, rather than using a higher grade of gas. If switching to high octane improves mileage, it may mean that your engine, or its control system needs repair.

The higher the octane, the higher the price. Gas stations make more money on high-octane gas, than the regular grade gasoline. Car manufactures, and automotive engineers, say assuming a vehicle will run better on a higher grade of gas than recommended, is throwing money away. It’s advisable to use the regular gasoline, if it’s required for your vehicle. By decreasing from premium to regular, you can save 20 cents per gallon. If you use the recommended octane level, then you will save 40 cents a gallon, or eight dollars on a 20 fill-up.

High octane costs more, and doesn’t improve your vehicle’s performance. With gas prices so high, it’s not worth the money. Vehicle owners should read their owners manuals, and think before choosing the higher grade of gasoline. The savings between low octane and higher-octane gasoline may seem like pennies, but consumers will be happy, when those pennies add up to be dollars. If, your vehicle doesn’t require the higher-octane gas, then don’t waste your time pumping it.

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For more on octane, visit How Stuff Works.