Auto Trader NZ
Published 28 February 2025
Have you ever pulled up to a fuel station, glanced at the pump, and wondered what those numbers actually mean? If you’re like most drivers, you’ve probably seen numbers like 91, 95, and 98 but never really given them much thought. However, these numbers play a crucial role in determining how your car performs and what fuel is best suited for your engine. Let’s break it down.
Understanding Octane Ratings
The numbers you see on the pump—91, 95, and 98—represent the octane rating of the fuel. The octane rating measures a fuel’s ability to resist “knocking” or “pinging” during combustion. Knocking occurs when fuel combusts prematurely in an engine, which can cause damage over time.
91 Octane – Regular Unleaded
This is the most common fuel type in New Zealand and is suitable for most standard petrol vehicles. It’s the cheapest option and works well for engines designed to run on regular unleaded fuel. If your car manufacturer specifies 91, there’s no real benefit in using a higher-octane fuel.
95 Octane – Premium Unleaded
A step up from 91, 95 octane fuel is designed for engines that require a higher resistance to knocking. Some vehicles, particularly those with turbocharged engines or European models, recommend 95 for optimal performance and fuel efficiency.
98 Octane – High-Performance Fuel
98 octane is considered a premium fuel and is ideal for high-performance and sports cars. It provides the highest resistance to engine knocking and can slightly improve efficiency and power in engines designed for it. However, if your car isn’t built to use 98, you won’t see significant benefits by using it over 91 or 95.
What About Diesel?
If you drive a diesel vehicle, you won’t see octane numbers. Instead, diesel pumps are simply labeled Diesel, and quite often marked as ‘D’. Unlike petrol, diesel doesn’t rely on spark ignition but rather compression ignition, meaning octane ratings aren’t relevant.
Can You Use a Higher Octane Than Recommended?
Using a higher octane fuel than recommended won’t harm your car, but it won’t necessarily improve performance or efficiency either—unless your engine is designed for it. It’s best to follow your manufacturer’s recommendation to avoid unnecessary costs.
What Happens If You Use the Wrong Fuel?
- Using a lower octane than required (e.g., putting 91 in a car that needs 95) can cause knocking, reduced performance, and potential engine damage.
- Using petrol in a diesel engine can cause serious damage and require costly repairs. If you accidentally misfuel, do not start the car—seek assistance immediately.
The Bottom Line
Understanding fuel pump numbers can help you choose the right fuel for your car, ensuring it runs smoothly and efficiently. Always check your owner’s manual or the inside of your fuel cap to see the recommended fuel type, and stick to it. Whether you’re filling up with 91, 95, or 98, using the right fuel will keep your engine in top shape and prevent unnecessary expenses down the line.
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