What kinds of petrol are there?
The numbers are the most relevant. Standard unleaded petrol is 91. Premium unleaded is both 95 and 98. The ethanol-blended e10 (a mixture of up to 10% ethanol in petrol) is a substitute for 91 in most cars. Those numbers – 91, 95 and 98 – encompass the octane rating of the fuel. They’re all about the same in terms of the energy in the fuel. Really octane is a measure of how much heat and pressure a fuel can withstand before igniting.
Manufacturers design engines for a minimum octane rating. If you open the fuel flap of your car and it says “unleaded petrol only” it means 91 octane fuel is okay to use. If it says “premium unleaded only” it means you need to use at least 95. If the fuel flap tells you to use 98, you use 98.
Can I put a higher octane fuel in my car?
It won’t hurt your engine if you use a higher octane fuel. For example, if you use 95 or 98 in an engine designed for 91, that’s fine. However, avoid using a lower octane fuel than the minimum recommended by the manufacturer. Using 91 in an engine designed for 95 or 98 is potentially destructive.
High-octane petrol, often labelled premium or supreme, sounds as if it should rank mightily above plain old regular. Fuel retailers say that it improves overall performance and engine efficiency. Retailers aren’t lying, but they do sometimes overstate the benefits. Most engines will adapt very slightly if you run them on a higher octane fuel than the minimum recommended.
But in practice, the improvement is small, and the price premium of the higher octane fuel always eclipses the economy benefit from running it. In other words, it’s not an economically rational choice to run 98 in an engine designed for 91, even though it might run slightly better. The small increase in fuel economy isn’t enough to overcome the extra cost. A premium tag doesn’t mean the fuel is better quality, as all petrol sold in New Zealand has to meet strict quality levels.
While it might appear that using a higher octane petrol than specified for your vehicle might unleash some hidden power within your engine, you’re not really doing anything for it. Most cars in NZ are designed to run on 91 octane fuel.
What about e10?
Ethanol is an octane booster and can enhance performance, but the slight negative is there can be around a 3% increase in fuel consumption. It isn’t a substitute for premium unleaded petrol. If your car requires 95 or 98, e10 is not a viable fuel for it. The majority of cars on New Zealand roads designed for 91 petrol can accept e10 – but you should check the owner’s manual or ask the manufacturer or dealer first.
What’s the word on fuel prices?
The New Zealand government released its proposed changes to the Fuel Market Bill earlier this year. It followed a Commerce Commission fuel market study, which found motorists are paying more than they should for petrol. The report found companies are making high profits due to a lack of competition in the industry.
The government will introduce changes it says will promote greater competition in the fuel market at the wholesale level, ideally leading to lower prices for motorists. Their focus on making changes at the wholesale level are intended to grant smaller players, such as Waitomo and Gull, access to cheaper fuel.
Regulatory changes in the Fuel Market Bill currently being updated include a more transparent wholesale pricing regime, and rules to ensure contracts between wholesale fuel suppliers and their customers support competition. It would require the three largest companies, Mobil, BP and Z, to publicly advertise the wholesale price of the fuel coming through their terminals.
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