E10 fuel vs unleaded comparison test
For most drivers in Australia, the fuel pump is a necessary evil, but few understand how much the liquid in the tank has evolved beyond simple petroleum. While diesel and LPG serve specific roles, petrol comes in several forms, the most prominent being the widely available E10. The shift from traditional unleaded to ethanol blends has significant implications for vehicle performance, fuel economy, and engine longevity.
Understanding the Numbers
Drivers encounter terms like 91RON, 95RON, and 98RON at the pump, which refer to the fuel’s octane rating. The Research Octane Number measures the fuel’s ability to resist knocking or detonation. While the metric system is standard in Australia, the American scale relies on Motor Octane Numbers, which can lead to confusion for international travelers. In general, a higher number indicates a higher quality of fuel, though the practical impact varies by vehicle.
Historically, the market offered three primary grades: 91RON (unleaded), 95RON (premium unleaded), and 98RON (Ultra Premium Unleaded Petrol). Basic cars often ran efficiently on the cheaper 91RON, while European imports required the higher 95RON. Performance vehicles typically relied on 98RON for its superior cleaning properties and combustion stability.
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The Rise of E10
E10 has largely replaced the old 91RON standard. The “E” stands for ethanol, an alcohol blend designed to make fuel production more environmentally friendly. This fuel consists of 90 per cent unleaded petrol mixed with 10 per cent ethanol. The ethanol helps boost the octane rating to 94RON, but it also increases fuel consumption due to its lower energy density compared to pure petrol.
For the average commuter, the primary consideration is cost versus efficiency. E10 is usually cheaper than 95 or 98, but because you burn through it faster, the savings can sometimes evaporate quickly. The choice of fuel is ultimately a balancing act between the price at the bowser and the specific requirements of the engine sitting in the driveway.
Choosing the right fuel requires a quick check of the owner’s manual or the label on the inside of the fuel door. Manufacturers set minimum grade requirements to ensure the engine runs smoothly and to prevent damage. For vehicles built before 1986, which originally ran on leaded fuel, ethanol is not recommended. The alcohol can degrade rubber hoses and seals, leading to gum buildup that stops the engine from starting. Modern 98RON UPULP, however, is safe for these older engines.
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High-Octane and High-Performance Options
Some drivers believe using 98RON in a standard car will improve performance or save money. In reality, unless the car has been specifically tuned for high-octane fuel, the vehicle will not produce more power or better mileage. Any efficiency gains from 98RON are usually due to its cleaning agents removing carbon deposits that were already restricting the engine’s performance.
High-performance vehicles, including models from Porsche, Ferrari, and certain AMG or M Sport trims, are tuned to take advantage of high-octane fuel. These engines run hotter and have stricter tolerances, making them more prone to detonation or knocking. Using a fuel with a lower octane rating than recommended in extreme heat can cause this dangerous ignition, potentially leading to serious engine damage. Detonation is difficult to hear or feel, so relying on the manufacturer’s recommended grade is the safest approach.
E85 represents another option, boasting a blend of 85 per cent ethanol. Once hailed as a sustainable alternative, E85 has struggled to gain traction due to its poor burn-rate and scarcity. For modified cars specifically set up to run on it, E85 can allow for lower operating temperatures and increased power, but it typically reduces fuel economy by 30 per cent. Using E85 in a standard vehicle not designed for it can destroy fuel system components in a matter of minutes.
