Are you sure you're filling your car with the correct petrol? It pays to check as the petrol you use may not agree with the engine. Some cars will not perform at their best if they do not run on premium fuel.
Each fuel comes with an octane rating - 91, 95 etc. - which indicates the percentage of octane found in the fuel.
Communications manager for BP New Zealand Jonty Mills tells Driven, "Premium has a higher octane than regular. In simple terms, the higher the octane, the more power and more resistance."
Premium fuel has a refining process which includes the addition of different components not used in regular unleaded.
Although any petrol car is able to run on premium fuel, it does pay to check if your engine is compatible.
"People need to refer to their vehicle manuals. The OEMs [engine manufacturers] are best placed to confirm the fuel type that best suits their engines," he says.
A label can be found on the inside of your fuel filler cap or around the filler, indicating what fuel your car runs best on.
If you feed an engine with an insufficient amount of octane, it will knock. Also known as detonation, knocking is an uncontrolled combustion which happens before the sparkplug generates a spark.
With older engines, heavy cases of knock can lead to a piston being damaged or destroyed, if left unchecked.
Modern engines come with a knock sensor. This detects the slightest ping from knocking and dials back on ignition timing to get rid of it before we hear it.
If your car runs on premium fuel, the knock sensor will have almost nothing to detect. The octane rating is a measure of its resistance to knock and using premium ensures the flow of fuel will be smoother and more consistent.
Premium fuel also has cleaning properties to keep your engine clean. By using detergency products with the ability to remove existing engine deposits, your engine gets a clean every time you fill up.
More aggressively tuned high-performance engines also benefit from using premium as more power is generated from each litre of gas.
Your engine is also better protected against corrosion and wear in key engine components.
Although regular 91 octane unleaded still sells well, demand is rising for premium fuel. "On average the NZ car fleet is older, therefore still a high demand for 91, but the demand for 95 and 98 grades is growing," says Mills.
If it is compatible with your car's engine, then it's worth paying the extra for premium fuel. And, yes, premium diesel is on offer, too.