Which Fuel Should I Use in My Car?

Putting the right fuel in your car is simpler than the pump board makes it look — it comes down to one number the manufacturer chose for your engine. Here's how to find it, and how to avoid the costly mistakes.

How do I know which fuel my car takes?

Two places tell you, and they beat any guess:

1. Inside the fuel filler flap — most cars print the required or recommended fuel there (e.g. "Unleaded 91 minimum", "Premium unleaded only")
2. The owner's manual — the fuel section states the minimum octane and whether E10 is approved

If they disagree or you're unsure, follow the higher requirement and check with the manufacturer.

What does 'minimum 91 RON' mean?

It means your engine is designed to run safely on 91 or anything higher. So you can use:

• 91 (regular unleaded)
• E10 — if your car is also listed as E10-compatible (see E10 explained)
• 95 or 98 — allowed, but usually little benefit in an engine built for 91

If the flap says "Premium unleaded only" or "95 minimum" / "98 minimum", don't drop below that octane — see Is premium worth it?.

Can I use a higher octane than my car needs?

Yes — running 98 in a car that only needs 91 won't harm the engine. But it usually won't help either: an engine tuned for 91 can't exploit the extra knock resistance, so you're mostly paying more for no gain. Higher octane only pays off in engines designed for it. More on why: What is RON?.

Petrol or diesel — how do I avoid misfuelling?

Petrol and diesel are never interchangeable, and putting the wrong one in can cause serious, expensive damage.

• Diesel cars take diesel only; petrol cars take petrol only.
• If you realise you've filled with the wrong fuel, do not start the engine — that's what spreads the damage. Leave the car, and call roadside assistance or your motoring club to have the tank drained.

Diesel nozzles are larger than petrol nozzles, which helps prevent diesel going into a petrol car, but the reverse can still happen — slow down at the bowser and check the pump before you lift the handle.

What about E85, LPG and E10?

• E10 — a 91-compatible ethanol blend, but only if your car is E10-approved: E10 explained
• E85 — for flex-fuel and specially modified vehicles only, sold at few stations: Find E85 stations
• LPG — for dual-fuel or converted vehicles: LPG prices Australia

Never run E85 or E10 in a car not rated for it.

Set your fuel in Petrol Australia

Once you know your fuel, set it as your default in the app (Profile → Preferences → Preferred fuel) so the map always shows prices for the fuel you actually buy — and add your vehicle for accurate savings maths (Set up your vehicle).

Related: What is RON? · E10 fuel explained · Premium fuel — 95 vs 98

Set your fuel and compare prices — download Petrol Australia for iPhone and Android at petrolaustralia.com.au.