Standing at the bowser with four or five fuel options can be confusing. E10, Unleaded 91, 95, 98… what’s the difference? And more importantly, which one should you put in your car? This guide breaks down everything you need to know.
Understanding Fuel Types in Australia
Australian petrol stations typically offer several fuel grades. The number (91, 95, 98) refers to the octane rating – a measure of the fuel’s resistance to “knocking” or premature ignition. E10 contains 10% ethanol blended with 90% unleaded petrol.
| Fuel Type | Octane Rating | Typical Price Difference |
|---|---|---|
| E10 | 94 RON | 3-5¢ cheaper than 91 |
| Unleaded 91 | 91 RON | Base price |
| Premium 95 | 95 RON | 10-15¢ more than 91 |
| Premium 98 | 98 RON | 20-30¢ more than 91 |
| E85 | 105 RON | Varies (flex-fuel only) |
E10 Fuel Explained
E10 is regular unleaded petrol blended with 10% ethanol. In Australia, the ethanol is primarily made from sugarcane and wheat – both renewable sources. It’s the cheapest fuel option at most stations.
E10 Pros
- Cheapest fuel option (3-5¢ per litre savings)
- Lower carbon emissions
- Supports Australian farmers
- Renewable fuel source
- Compatible with most cars made after 2005
E10 Cons
- Slightly lower energy content (~3% less)
- May reduce fuel economy by 1-3%
- Not compatible with all vehicles
- Can attract moisture over time
- Some older engines may have issues
Is E10 Worth It?
If E10 is 4 cents cheaper and you lose 2% fuel economy, you’re still saving money on a typical 50L fill. The savings are small but add up over time – around $50-100 per year for average drivers.
Premium Fuels (95 & 98) Explained
Premium fuels have higher octane ratings, which means they’re more resistant to knocking. But here’s the key question: does your car actually benefit from premium fuel?
When Premium Makes Sense
- Your car requires it – Check your fuel flap or owner’s manual. If it says “Premium Unleaded Only” or “95 RON minimum”, you need premium.
- Turbocharged engines – Most turbo cars require 95 or 98 RON for optimal performance.
- High-performance vehicles – Sports cars and performance engines are tuned for premium fuel.
- European cars – Many German, Italian, and other European vehicles require 95+ RON.
When Premium is a Waste
If your car is designed for 91 RON, putting in 98 won’t give you more power, better fuel economy, or a cleaner engine. The car’s computer is tuned for regular fuel – premium just costs you more money for zero benefit.
Common Myth
“Premium fuel cleans your engine better.” This isn’t true. All Australian fuels contain detergent additives that keep engines clean. Premium doesn’t clean better than regular unleaded.
What Does Your Car Actually Need?
The easiest way to know is to check:
- Inside your fuel flap – Most cars have a sticker listing recommended/required fuel
- Owner’s manual – Look in the specifications section
- Manufacturer website – Search your model’s specifications
You’ll see one of these terms:
- “Minimum 91 RON” – Use 91, E10, or any higher grade
- “Premium Unleaded Required” or “95 RON minimum” – Don’t use 91 or E10
- “98 RON recommended” – 95 is okay, but 98 gives best performance
Don’t Use E10 If…
Your car was made before 2005, or the manufacturer specifically says E10 is not compatible. Using E10 in incompatible vehicles can damage fuel lines, seals, and engine components. Check the FCAI website for a compatibility list.
Fuel Economy Comparison
Here’s how different fuels typically affect your fuel economy:
| Fuel Type | Relative Economy | Notes |
|---|---|---|
| E10 | 97-99% | 1-3% worse than 91 due to lower energy content |
| Unleaded 91 | 100% (baseline) | Standard reference point |
| Premium 95 | 100-102% | Slight improvement in cars tuned for it |
| Premium 98 | 100-103% | Best economy in cars requiring premium |
Important: These improvements only apply if your car is designed for premium fuel. A car tuned for 91 RON won’t see any economy benefit from 98.
The Real Cost Comparison
Let’s do the maths on a typical 50L fill, assuming Unleaded 91 costs 165.0¢/L:
| Fuel Type | Price/L | 50L Fill Cost | Annual Cost (1000L) |
|---|---|---|---|
| E10 | 161.0¢ | $80.50 | $1,610 |
| Unleaded 91 | 165.0¢ | $82.50 | $1,650 |
| Premium 95 | 177.0¢ | $88.50 | $1,770 |
| Premium 98 | 189.0¢ | $94.50 | $1,890 |
The difference between E10 and 98 is $280 per year – significant for most households. That’s why it pays to use the fuel calculators to work out what’s best for your situation.
Diesel: A Different Category
Diesel fuel works completely differently from petrol. Diesel engines use compression ignition rather than spark plugs, and diesel fuel has different properties entirely. Never put petrol in a diesel car or vice versa – it can destroy your engine.
If you drive a diesel, your main choices are standard diesel and premium diesel. Premium diesel typically contains additional cleaning additives and may improve performance slightly, but for most drivers, standard diesel is perfectly fine.
How Fuel Choice Affects the Price Cycle
All fuel types follow the same 42-day price cycle in Queensland. When prices spike, they spike across all grades. When they drop, all grades drop together – usually maintaining the same relative price differences.
This means the best strategy is to:
- Know which fuel your car needs
- Time your fill-ups to the bottom of the cycle
- Use Fuel Daddy to find the cheapest station for your fuel type
Quick Decision Guide
Which Fuel Should You Use?
Use E10 if:
- Your car is E10 compatible (most cars 2005+)
- You want to save money
- You prefer a lower environmental impact
Use Unleaded 91 if:
- Your car requires 91 RON minimum
- Your car isn’t E10 compatible
- You rarely drive and fuel sits in the tank for months
Use Premium 95/98 if:
- Your car requires it (check the fuel flap!)
- You have a turbocharged or performance engine
- Your manufacturer recommends it for best performance
Key Takeaways
- Check your fuel flap or owner’s manual to know what your car needs
- E10 is fine for most cars made after 2005 and saves you money
- Premium fuel only benefits cars designed for it – don’t waste money
- Using lower octane than required can damage your engine
- Using higher octane than required just wastes money
- All fuel types follow the same price cycle – time your fill-ups