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 higher than the 91 RON rating of standard Unleaded 91.
E10 vs Unleaded 91 at a glance
| Question | E10 | Unleaded 91 |
|---|---|---|
| Typical pump price | Usually 3-5c/L cheaper than U91 | Usually dearer at the bowser |
| Energy content | About 3% less energy per litre in a 10% ethanol blend | Higher energy content per litre |
| Octane rating | Minimum 94 RON | 91 RON |
| Best for | Compatible cars when the discount is 4c/L or wider | Cars not approved for ethanol, infrequent driving, and narrow price gaps |
| Main risk | Not suitable for some older vehicles, motorcycles, boats and small engines | May cost more per tank when E10 is heavily discounted |
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. The pump price alone does not settle the choice, because E10 can use slightly more litres for the same distance.
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, a 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, which is nearly identical.
Break-even rule for E10 vs U91
For most E10-compatible cars, a 4c/L discount is the practical break-even point. If E10 is 5c/L or more cheaper than U91, E10 usually wins on cost per kilometre. If the gap is below 3c/L, Unleaded 91 is usually better value because the small pump saving is eaten by the fuel economy drop. Between 3c/L and 4c/L, the answer depends on your car, driving mix and tank size.
Can your car use E10?
Most petrol vehicles manufactured from 2005 onwards are approved for E10, including many Toyota, Mazda, Hyundai, Kia, Ford and Holden models. Check your owner's manual, the sticker inside your fuel filler flap, or the Federal Government's E10 compatibility guidance. Vehicles that should avoid E10 include models built before 2005, some European imports, many motorcycles and boats, and small engines like mowers and generators. E10 also absorbs moisture from the air, so avoid storing it 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, and you want a partially renewable fuel option. E10 makes the most sense for daily drivers who empty the tank regularly and can consistently find a meaningful discount.
Stick with U91 when: your vehicle is not approved for ethanol blends, the price gap is less than 3c/L, you are filling a car or equipment that sits unused for weeks or months, or your manufacturer specifically recommends non-ethanol fuel.
How to compare E10 and U91 near you
Compare live E10 and U91 prices before each fill because the gap changes by suburb, brand and price-cycle phase. The cheapest E10 station is not always the cheapest station after economy is considered, and a discounted U91 station can beat nearby E10 when the cycle is falling. Use the live FuelRadar map to check both fuels, then choose based on the current cents-per-litre gap and your vehicle compatibility.
The bottom line
E10 is the better-value fuel when your car supports it and the discount is wide enough. Use this rule: 5c/L cheaper means E10 is usually worth choosing, 4c/L is roughly break-even, and below 3c/L U91 is usually safer value. Compatibility comes first; never use E10 in a vehicle, boat, motorcycle or small engine that is not approved for ethanol blends.
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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