What Happens if You Don't Use Premium Gas in a High Performance Sports Car?
Due to their high-performance engines, sports cars often require premium gas, making trips to the pump even more painful. Even with the "Premium Only" label staring at you every time you open the fuel door, it can be tempting to fill the tank with regular-grade gasoline instead. While doing so may save you a few dollars on each fill-up, it can cost you a lot more in the long run because of numerous performance and reliability issues that arise when using fuel with a lower octane rating than the manufacturer suggests. Furthermore, regular-grade gasoline is likely to decrease a high-performance engine's fuel economy, effectively making it more expensive to drive per mile compared with using premium fuel.
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Octane Ratings
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Octane ratings are a measure of a fuel's tendency to ignite. The higher the octane rating, the more resistant the fuel is to combustion. For this reason, premium fuels can withstand a greater amount of heat and pressure before ignition occurs. Since power is generated through combustion, this property may seem counterintuitive, given that premium fuels with lower combustibility are most commonly used in high-output engines. However, once you understand the basic inner workings of an engine, the need for higher octane in performance applications becomes evident.
Generating High Performance
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The way gasoline engines generate horsepower is through an internal combustion process in which an air and fuel mixture is compressed and ignited. As a rule of thumb, this means that the more air and fuel you can cram into an engine for each combustion cycle, the more power it will generate. Performance engines employ techniques such as high-compression pistons and forced-induction systems to achieve a more powerful combustion process, and thus horsepower output is increased. There's a downside, though, because increased power means increased heat and pressure in the cylinders.
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Premium Requirements
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In general, roughly 60 percent of the energy released in the combustion process turns into heat. With a performance engine, the increased temperature and pressure in the cylinders makes it more likely the air-fuel mixture will detonate prior to the spark plug firing. Another issue that can arise is engine knocking, a situation in which pockets of fuel left over after combustion are ignited. Since premium fuel has a higher combustion temperature than regular fuel, it reduces the risk of these unwanted detonations occurring.
Performance Effects
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Engine knock and pre-ignition can ruin the performance of an engine. Since these detonations occur when the engine is not at top dead center, the energy generated is counter to the natural motion of the pistons and crank. This not only decreases horsepower and engine smoothness, it also raises the pressure in the cylinders, which increases the stress on internal components. Furthermore, most engines feature knock sensors and other electronic monitoring systems. When detonations occur, the ECU adjusts the engine timing, fuel tuning and other parameters to compensate. This will further reduce horsepower, as well as decrease the engine's fuel economy.
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References
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