Pull into almost any Australian servo and you face a row of coloured nozzles: E10, U91, U95, U98, diesel and sometimes LPG. Six labels, six different prices, and no obvious explanation of which one your car actually wants. It is exactly the kind of everyday fuel confusion FueVolt exists to clear up.
Each nozzle represents a fuel with distinct properties, price points and engine compatibility. Picking the right one matters for your engine's health and your wallet, and it is not as complicated as the labels make it look. In Australia, the properties of each fuel are set in law under the Fuel Quality Standards Act 2000, administered by the Department of Climate Change, Energy, the Environment and Water — so a litre of U95 at one servo has to meet the same standard as U95 anywhere else.
Unleaded 91 (U91)
U91 is the baseline unleaded petrol in Australia. The number 91 refers to its Research Octane Number (RON), which measures resistance to engine knock. Most passenger cars manufactured before 2005 and many budget models run perfectly well on U91. It is almost always the cheapest petrol option at the bowser.
Ethanol Blend E10
E10 is unleaded petrol blended with up to 10 per cent ethanol derived from sugar cane or grain. It typically carries a RON of 94 and costs a few cents less per litre than U91. Not every car is compatible with E10 — check your owner's manual or the fuel flap sticker. If your car accepts it, E10 is often the most cost-effective choice.
Premium 95 (U95)
Premium 95 has a higher octane rating than U91, which means it resists pre-ignition (knocking) better under load. Many modern turbocharged four-cylinder engines, European cars and some Japanese imports require a minimum of 95 RON. Using a lower-octane fuel in these engines can trigger the knock sensor and reduce performance.
Premium 98 (U98)
U98 is the highest-octane petrol widely available in Australia. High-performance and luxury vehicles often specify 98 RON for optimal power delivery and efficiency. While it costs the most per litre, drivers of compatible cars may see slightly better fuel economy because the engine can advance timing further.
Diesel
Diesel fuel powers compression-ignition engines common in SUVs, utes, trucks and some passenger cars. Diesel engines are more thermally efficient than petrol engines, meaning they extract more energy per litre, which translates to longer range. However, diesel has been more expensive than petrol in recent years due to refining costs and global demand.
Premium Diesel
Some stations sell premium diesel with added detergent and cetane-boosting additives. The higher cetane number means smoother combustion and potentially better cold-start behaviour. Whether the extra cost is worthwhile depends on your driving style and engine age.
LPG (Liquefied Petroleum Gas)
LPG is a mix of propane and butane stored under moderate pressure. It burns cleaner than petrol with lower carbon dioxide emissions. The trade-off is roughly 15 to 20 per cent lower energy density, so you use more litres per hundred kilometres. LPG is significantly cheaper per litre, which often offsets the higher consumption. Fewer new cars come with factory LPG systems today, but many older Falcons and Commodores have aftermarket conversions.
Which Fuel Should You Use?
Always follow the minimum octane rating specified by your vehicle manufacturer. The Green Vehicle Guide lists the recommended fuel type for most models sold in Australia if you are unsure. Using a higher octane than required will not damage your engine but usually provides no measurable benefit in a standard car. Using a lower octane than required can cause knocking, reduced power and potential engine damage over time.
Check the fuel flap or owner's manual to confirm your car's requirements before filling up.
How the Fuels Compare on Price
Grades are not priced in equal steps. In a snapshot of Brisbane-area stations in September 2026, the cheapest E10 was 213.5 cents a litre, the cheapest U91 was 215.5, the cheapest U95 was 234.5 and the cheapest U98 was 237.5. The cheapest diesel was 264.9, about 49 cents above the cheapest U91.
Two things stand out. First, the jump from U91 to U95 (about 19 cents) was far bigger than the jump from U95 to U98 (about 3 cents). Second, E10 was only about 2 cents cheaper than U91 at the cheapest stations, and about 3 cents cheaper on average across the area. Because ethanol carries slightly less energy than petrol, an E10-compatible car may use a little more fuel per kilometre, so a small price gap can shrink to almost nothing in real terms.
That is one snapshot, and prices change daily, so the useful habit is to compare grades on the day you fill up. The fuel prices page lets you switch fuel type and see the cheapest stations for each.
Can You Mix Fuels?
Different grades of petrol are safe to mix. If you put U91 in a tank that is half full of U95, the result is simply a blend in between. Petrol and diesel, however, must never be mixed, and neither must be used in the wrong type of engine.
What If You Put the Wrong Fuel In?
Putting diesel in a petrol car, or petrol in a diesel car, is a common and expensive mistake. If you realise at the bowser, do not start the engine. If you notice after driving off, pull over safely and switch it off as soon as you can. Turning the ignition on can prime the fuel pump and circulate the wrong fuel through the system. Call roadside assistance and have the tank drained before the car is driven again. Either mistake can damage the fuel system and engine, and the damage grows the further you drive.
Using E10 in a car that is not compatible is less dramatic, but you should switch to the correct fuel at the next fill and check your owner's manual. Some older cars, motorcycles and small engines are not suited to ethanol blends.
AdBlue Is Not Fuel
Many newer diesel vehicles need AdBlue, a separate exhaust treatment fluid that lives in its own tank, usually with a blue cap near the fuel filler or under the bonnet. It is not a fuel additive. Never pour it into the fuel tank, and never put diesel in the AdBlue tank. AdBlue is sold at many service stations and auto shops.
Not Every Station Sells Everything
Stations do not all stock every fuel. LPG in particular is sold at a limited number of sites, and premium diesel and U98 are less common at smaller stations. FueVolt shows the fuels each station reports to the state government price schemes, so if you rely on LPG or another less common fuel, check that a station lists it before you detour.