E10 vs U91: Which Fuel Should You Use?
Is E10 worth it? We break down the real price difference, fuel economy impact, and which Australian cars can safely use ethanol-blended petrol.
E10 is almost always the cheapest petrol at the bowser. But is it actually cheaper once you account for the lower fuel economy? And can your car even use it? Let's break it down.
What is E10?
E10 is regular unleaded petrol (91 RON) blended with 10% ethanol. The ethanol is mostly produced from sugarcane or grain in Australia. It's been widely available since the mid-2000s and is now offered at most service stations in Queensland, New South Wales, and other states.
The "E" stands for ethanol, and the "10" means 10% of the blend is ethanol. The other 90% is standard petrol.
The price difference
E10 is typically 3–5 cents per litre cheaper than U91 (standard unleaded). On a 50-litre fill, that's $1.50–$2.50 less every time you fill up.
Over a year of weekly fills, that adds up to roughly $80–130 in savings. Not life-changing, but not nothing either — especially stacked on top of other fuel-saving habits.
The fuel economy trade-off
Here's the catch: ethanol contains about 30% less energy per litre than petrol. Since E10 is 10% ethanol, it has roughly 3% less energy per litre than U91.
In practice, this means your car's fuel economy (L/100km) will be about 3% worse on E10. For a car averaging 10 L/100km on U91, you'd average about 10.3 L/100km on E10.
Does the price saving still stack up?
Let's do the maths for a typical scenario:
- U91 price: 180.0 c/L
- E10 price: 175.0 c/L (5c cheaper)
- Fuel economy on U91: 10.0 L/100km
- Fuel economy on E10: 10.3 L/100km
For 100km of driving:
- U91 cost: 10.0L × $1.80 = $18.00
- E10 cost: 10.3L × $1.75 = $18.03
Almost identical! When E10 is only 5c/L cheaper, the savings are nearly wiped out by the lower economy. When E10 is 3c/L cheaper, you're actually paying slightly more per kilometre.
The real saving comes when E10 is 5+ cents cheaper than U91. At that point, the maths tips in E10's favour. You can check the current price gap on BowserBuddy by switching between E10 and U91 in the fuel type dropdown.
Can your car use E10?
Most cars made after 2006 can use E10 safely. But not all. Here's how to check:
- Look at the fuel flap — many cars have a sticker listing compatible fuel types
- Check the owner's manual — it will list the minimum RON and whether ethanol blends are approved
- Check the FCAI list — the Federal Chamber of Automotive Industries maintains a vehicle compatibility list for E10
Cars that should NOT use E10:
- Older cars (pre-2006) not specifically approved for ethanol
- Many European cars (some BMWs, Mercedes, Volkswagens) unless the manual says otherwise
- Small engines — lawnmowers, chainsaws, outboard motors
- Classic and vintage cars
Using E10 in an incompatible car can damage fuel system components (seals, hoses, fuel pump) over time. If in doubt, stick with U91.
Cars that CAN use E10:
- Most Toyota, Mazda, Hyundai, Kia models from 2006 onwards
- Most Ford, Holden (RIP), Mitsubishi models from 2006 onwards
- Most modern Subaru, Honda, Nissan models
- Check your specific model to be sure
What about E85?
E85 is a high-ethanol blend (85% ethanol) that's only compatible with flex-fuel vehicles. Very few cars in Australia are flex-fuel, and very few stations sell E85. It's a completely different product from E10 — don't confuse the two.
What about premium fuels (U95, U98)?
If your car's minimum requirement is 91 RON, using U95 or U98 won't give you any noticeable benefit. Premium fuels are designed for high-performance engines with higher compression ratios. For a deeper comparison, see our guide to diesel vs petrol running costs.
The exception: some cars recommend (but don't require) premium. In these cases, premium might give slightly better performance and economy, but U91 or E10 will work fine for everyday driving.
The verdict
E10 is a reasonable choice if:
- Your car is compatible (check the fuel flap)
- The price gap is at least 5 cents per litre below U91
- You want to save ~$80–130 per year without changing your habits
Stick with U91 if:
- Your car isn't approved for ethanol
- The price gap is less than 3 cents (the economy difference cancels it out)
- You want the simplest option without thinking about it
Either way, the biggest savings come from comparing prices between stations, not from choosing between fuel types. A 15c/L difference between two stations selling U91 dwarfs the 3–5c/L E10 discount.