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Why is ethanol used as an additive in gasoline?
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Ethanol is added to gasoline primarily to increase its octane number, which improves the fuel's antiknock characteristics and results in a smoother-running engine.12
Beyond its performance benefits, ethanol is used as an additive for several key reasons:
- Renewability: Ethanol can be produced from plant matter such as grains, potatoes, and sugarcane, making it a desirable, renewable alternative fuel source.134
- Emissions: Ethanol is considered a cleaner-burning fuel, which can help reduce certain vehicle emissions.32
- Economic and Strategic Factors: The use of ethanol, often in a mixture known as gasohol, gained prominence in the late 20th century as a response to rising petroleum prices.14
While ethanol offers these advantages, it has a lower energy density than pure gasoline, which can lead to a decreased driving range per tankful. Additionally, because ethanol can dissolve certain plastic parts, fuel systems must be designed to withstand its chemical properties.23