Can You Use Regular Unleaded If Your Car Requires Premium Fuel?

If you’ve ever been on a long road trip or just pulled into your usual petrol station only to find premium fuel unavailable, you might have wondered: Can I use regular unleaded instead? Or can I mix different fuel types?

The answer? It depends on your car’s requirements. Let’s break it down.

What Do the Numbers on Petrol Pumps Mean?

The Research Octane Number (RON) measures a fuel’s stability—the higher the RON, the more resistant the fuel is to auto-ignition or detonation under pressure.

Here’s how Australia’s fuel grades compare:

• 91 RON (Regular Unleaded) – Standard fuel, suitable for most cars.
• 95 RON (Premium Unleaded) – Required by some performance and turbocharged vehicles.
• 98 RON (Super Premium Unleaded) – Offers the highest resistance to knocking, used in high-performance engines.

Why Does Octane Rating Matter?

Using fuel with a lower octane rating than recommended can cause engine knocking—a knocking or pinging sound caused by uneven fuel detonation. Over time, this can lead to engine damage.

Can You Mix 91 with 95 or 98?

The short answer is yes and no—it depends on your car’s minimum requirements.

✅ If your car is designed for 91 RON fuel: You can safely mix 91, 95, or 98 without any issues.

🚫 If your car requires a minimum of 95 RON: You should NOT use 91 RON, even in a mix. Stick to 95 or 98.

🚫 If your car requires 98 RON: Always use 98 RON—mixing it with 91 or 95 could reduce performance and potentially harm the engine.

🔴 One thing you should NEVER do: Fill your petrol car with diesel—or vice versa. That’s a costly mistake!

What Are the Benefits of Premium Fuel?

Even if your car doesn’t require premium fuel, using higher-octane petrol can sometimes offer advantages:

🔹 More efficient combustion – Leading to a smoother drive.🔹 Optimised power delivery – Helps performance engines work at their best.🔹 Better fuel efficiency – Some cars may get more kilometres per litre with premium fuel.

According to the NRMA, premium fuel helps optimise an engine’s ability to make power through increased fuel density, reducing engine ping and ensuring smoother performance.

However, if your car only requires 91 RON, upgrading to 95 or 98 won’t necessarily make a huge difference—especially if your engine isn’t tuned for it.

What to Do If You Can’t Find Premium Fuel

If your car requires premium fuel but you can’t find any, consider these options:

✔ Use the highest RON available – If your car needs 98 RON, but only 95 RON is available, use 95 as a temporary solution.

✔ Top up with premium ASAP – If you’ve accidentally used lower-octane fuel, refill with the correct octane as soon as possible.

✔ Drive conservatively – Avoid hard acceleration and high RPMs until you can refuel with the proper fuel.

Final Thoughts

✅ Mixing fuel is okay, but only if your car allows it.✅ Always use at least the minimum octane rating recommended for your vehicle.✅ Premium fuel has benefits, but it’s not always necessary for cars designed for regular unleaded.✅ If you’re in a pinch, go for the next highest octane available.

So, next time you’re at the pump and your preferred premium fuel isn’t available, check your car’s fuel requirements before making a decision! 🚗⛽