1. What Is Ethanol in Fuel?
Ethanol in fuel refers to a gasoline blend that contains ethanol — an alcohol derived from fermenting crops like sugarcane, corn, or cassava.
Common blends include E10 (10% ethanol, 90% gasoline) or E20 (20% ethanol, 80% gasoline).
Ethanol is added to gasoline primarily to enhance combustion performance, reduce emissions, and decrease dependence on fossil fuels.
2. Relationship Between Ethanol in Fuel and Octane Rating (RON)
The Research Octane Number (RON) measures how well a fuel resists knocking — premature ignition inside an engine’s cylinder.
A higher RON means smoother combustion and better engine performance.
Ethanol naturally has a very high octane number — around RON 108.
When blended with gasoline, it raises the overall octane rating of the mixture.
For example:
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Pure gasoline RON 90 + 10% Ethanol → increases to around RON 92–93
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Gasoline RON 92 + 10% Ethanol → may reach RON 94–95
3. Why Ethanol in Fuel Increases RON
There are three main reasons why ethanol in fuel raises the octane rating:
a. Stable Chemical Structure
Ethanol contains a hydroxyl group (-OH) that stabilizes combustion, reducing the likelihood of knocking.
b. Slower and More Even Combustion
Ethanol vaporizes quickly and mixes evenly with air, creating a cleaner, more controlled burn inside the combustion chamber.
c. Cooling Effect in the Combustion Chamber
Ethanol absorbs more heat when it vaporizes (high latent heat of vaporization), creating a cooling effect that reduces the chance of pre-ignition and increases efficiency.
4. Pros and Cons of Ethanol in Fuel
Advantages:
- Increases octane rating (RON)
- Promotes cleaner and more efficient combustion
- Reduces harmful emissions
- Renewable — produced from bio-based sources
Disadvantages:
- Slightly lower energy density than pure gasoline (less power per liter)
- Can cause corrosion in engines not designed for ethanol
- Absorbs moisture from the air (hygroscopic), potentially lowering fuel quality over time
5. Effects of Ethanol in Fuel on Engines
Using ethanol-blended gasoline (like E10) is generally safe for modern engines designed to handle it.
However, for older engines or agricultural machinery not built for ethanol, it can cause:
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Reduced performance
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Rust or corrosion in fuel tanks
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Deterioration of rubber seals and hoses
For equipment such as generators, water pumps, or brush cutters, it’s best to use pure gasoline (non-ethanol) or fuels that meet the manufacturer’s recommendation to avoid damage.
6. Conclusion
Ethanol in fuel raises the octane rating (RON) thanks to its high combustion stability and cooling properties.
While it helps improve engine efficiency and reduce emissions, the type of engine and fuel system must be considered before use.
For agricultural and multipurpose machines, always check the recommended fuel type — and choose non-ethanol gasoline for maximum engine life and performance.
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