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E10 vs 91: Navigating your fuel choices

Mark Bristow avatar
Mark Bristow
- 5 min read
E10 vs 91: Navigating your fuel choices

If you want to keep your car running smoothly and avoid costly mechanic bills, then choosing the right fuel is important. In Australia, regular unleaded petrol (91), premium unleaded (95 and 98) and E10 are among the most common petrol choices for motorists. If you’ve seen these names on the petrol bowser without fully understanding what they mean, here are the basics to help you make a more informed choice the next time you fill up your car.

What types of fuel are available in Australia?

In Australia, the primary types of fuel available are:

  • Ethanol-blended unleaded petrol e.g. E10
  • Unleaded petrol e.g. 91 octane
  • Premium unleaded petrol e.g. 95 and 98 octane
  • Diesel

Each type is designed to meet specific engine requirements and environmental standards, and each can make a different impact on your car’s performance and efficiency.

What is the difference between unleaded 91, 95, and 98 petrol?

These Research Octane Numbers (RONs) refer to how efficiently these fuels combust and power your engine. The higher the number, the greater the performance you may be able to get from the fuel, though the more you may pay at the bowser. 

Unleaded 91 is the most common fuel type, and is suitable for most cars in Australia. It has an octane rating of 91, which is lower than some others on the market, and which means that it is generally suitable for petrol cars that do not have high performance requirements.

Premium Unleaded 95 and 98 are fuels with higher octane ratings than regular unleaded. They are more suitable for cars with high-performance or turbocharged engines that operate under higher pressures, and are generally more expensive at the bowser.

E10 is a blend of 10% ethanol and 90% unleaded petrol. It is generally not as fuel efficient as regular unleaded, meaning that your car’s petrol consumption may increase. However, E10 is also considered to produce lower emissions than regular petrol

Should you use premium fuel in your car?

Using premium fuel (95 or 98) in cars designed for regular unleaded petrol (91) usually doesn't offer any significant benefit in terms of performance or fuel economy, especially when you consider the higher costs of these fuel types. However, vehicles specifically designed to run on higher octane fuel can benefit from improved performance and efficiency.

Can you use E10 in your car?

Most modern cars are compatible with E10, but if in doubt, it’s important to check your vehicle's manual or fuel flap, or to contact the manufacturer. You could also use an online fuel compatibility checker. Some older vehicles may not be designed to use ethanol-blended fuels, leading to potential engine damage over time.

What if you use the wrong type of fuel?

Using the wrong type of fuel in your car can lead to a number of issues, which can end up causing damage to your car. Using E10 in non-compatible vehicles can cause corrosion or damage to the fuel system over time. Using Regular 91 in a vehicle that requires Premium 95 or 98 can lead to reduced performance and efficiency. It can even cause ‘engine knocking’, where pockets of air and fuel explode, often damaging your engine.

Diesel is most often used in utes, trucks and farm machinery. Diesel fuel pumps and fuel tanks are often sized and shaped differently to those for unleaded petrol, which may help reduce the risk of mixing up these fuel types. If a mixup does occur, and petrol goes in a diesel engine, or diesel goes in a petrol engine, the engine could be at serious risk of damage. It may be worth calling for roadside assistance or a tow to a mechanic to get the fuel drained from your vehicle. 

How can you save money on fuel?

If you’re wondering how to save some money at the bowser, some tips to consider include:

  • Choose the right fuel: Using the recommended fuel type for your vehicle can improve efficiency and prevent costly repairs.
  • Maintain your car: Regular maintenance, including tire pressure checks and engine tune-ups, can significantly improve fuel economy.
  • Drive efficiently: Accelerating gently, maintaining a steady speed, and avoiding unnecessary idling can help reduce fuel consumption.
  • Compare prices: Use fuel price comparison apps to find the cheapest fuel in your area.

When choosing fuel at the bowser, it’s important to consider your car’s specific requirements and what you want to get out of it. While E10 can be a cost-effective and environmentally friendlier option for compatible vehicles, premium fuels may offer benefits for certain high-performance engines. Always refer to your vehicle's manual and manufacturer recommendations to ensure optimal performance and longevity. You might even be able to save on fuel costs and potentially reduce some of your car’s impact on the environment.

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Product database updated 30 May, 2024

This article was reviewed by CEO Paul Marshall before it was published as part of RateCity's Fact Check process.