Fuel guide
E10 vs Unleaded 91 (U91) | Cost per KM, Economy & Compatibility
E10 vs 91 explained: price difference, fuel economy, compatibility, and when to choose each for Australia drivers.
At a glance
Key takeaways
E10 is typically 3-5c/L cheaper than U91 at the pump.
E10 contains 3% less energy per litre — most drivers see a 1-3% fuel economy drop.
Most vehicles built after 2005 are E10-compatible — check your owner's manual or fuel flap.
When the E10 discount is 4c/L or more, it usually saves money despite the efficiency loss.
What exactly is E10?
E10 is a blended fuel containing up to 10% ethanol and 90% regular unleaded petrol. The ethanol is produced from renewable sources — primarily sugarcane and grain in Australia — making it a partially renewable fuel. E10 carries a minimum octane rating of 94 RON, which is actually higher than the 91 RON of standard Unleaded 91.
What does E10 cost at the pump?
Across Australia, E10 is typically priced 3-5 cents per litre below Unleaded 91. On a 50-litre fill, that saves $1.50-$2.50 at the pump. Over a year of weekly fills, the raw pump saving is approximately $78-$130. However, the pump price alone does not tell the full story — you need to consider fuel economy.
The real cost per kilometre
Ethanol contains about 34% less energy per litre than pure petrol. In a 10% blend, that works out to roughly 3% less energy overall. Most drivers see a 1-3% drop in fuel economy with E10. Here is the real-world maths: assume U91 at 180.0c/L and E10 at 176.0c/L (4c/L gap). A car that uses 8.0L/100km on U91 will use roughly 8.24L/100km on E10. That means U91 costs $14.40/100km and E10 costs $14.50/100km — nearly identical. When the price gap widens to 5c/L or more, E10 saves money per kilometre. When it narrows below 3c/L, U91 is usually cheaper per kilometre.
Can your car use E10?
Most petrol vehicles manufactured from 2005 onwards are approved for E10, including popular brands like Toyota, Mazda, Hyundai, Kia, Ford and Holden. Check your owner's manual, the sticker inside your fuel filler flap, or the Federal Government's E10 compatibility website. Vehicles that should avoid E10 include models built before 2005, some European imports (older BMW, Mercedes, VW), many motorcycles and boats, and small engines like mowers and generators. E10 also absorbs moisture from the air — avoid storing E10 in a vehicle or equipment that sits idle for months.
When to choose E10 vs U91
Choose E10 when: your car is confirmed E10-compatible, the price gap is 4c/L or more, you drive regularly (no long fuel storage periods), and you want a partially renewable fuel option.
Stick with U91 when: your vehicle is not approved for ethanol blends, the price gap is less than 3c/L, you're filling a car or equipment that sits unused for weeks or months, or your manufacturer specifically recommends non-ethanol fuel.
Compare live prices
See E10 vs U91 prices near you.
Common Questions
Frequently asked questions
It depends on price and your car. E10 is usually 3-5c/L cheaper but has about 3% less energy. When the gap is 4c/L or wider, E10 is cheaper per kilometre for compatible cars; below 3c/L, U91 is usually better value.
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