Should I be using high-octane fuel?

Drive

Find out what octane is and how it affects the type of fuel you put in your car.

Fuel pumps with different octane levels.

Octane is a value that indicates the resistance of petrol to detonation or ‘knocking’.

That is, its ability to resist uncontrolled or explosive combustion within the engine’s combustion chamber that leads to excessively high pressures, pressure variations and high temperatures inside the engine that can quickly destroy engine parts including sparkplugs, pistons, head gaskets, and engine valves.

A driver may be able to detect ‘knock’ as a pinging or knocking noise coming from within the engine, often under hard acceleration from low speed.

Knocking can also occur at high speed, but that may well go undetected by the driver.

There are two measures of octane rating – Research Octane Number (RON) and Motor Octane Number (MON).

Both are important, with RON generally the number quoted at the service station forecourt and typically a higher number than the MON.

The higher the octane number, the more resistant to knock the fuel will be. And higher-octane fuels allow engineers to design more powerful and efficient engines.

Most cars sold here since 1986 have been built to accept Australia’s standard unleaded fuel of 91 RON.

Increasingly though, more vehicles are specifying high octane (premium) fuels, generally 95 RON minimum, with a few higher performance models needing 98 RON.

Your vehicle owner’s handbook will advise what octane fuel is required for your vehicle’s engine and it may also be found on a label on the fuel filler flap.

To prevent engine damage and drivability problems it’s vital you don’t use lower octane fuel than specified.

But will using a higher-octane fuel than specified provide benefits?

Some engines will perform better on a higher octane fuel, though others may show no discernible improvement.

On fuel injected cars it will depend on how ‘smart’ the engine management system is.

More sophisticated systems that can adjust fuel and spark maps to take advantage of the extra octane are the most likely to show improved performance, while less sophisticated engines generally won’t benefit.

Some reports suggest improved fuel economy on premium fuels, however it’s more likely to be vehicles that have ‘smart’ engine management systems that benefit, though it’s unlikely the gains will offset the premium fuel’s additional cost per litre.

 Older carburetted engines if specifically tuned for it may show limited gains, but otherwise will be unlikely to benefit. And very low-compression ratio engines may even run poorly on high octane fuels.

Some premium fuels have a different additive package intended to help keep fuel systems clean.

It’s a fairly subjective ‘seat-of-the-pants’ style test, but the only way to know will be to try a tank full of premium fuel and see the result.

In the end, the user will need to determine if any benefits are justified for the extra fuel cost.

Related topics

  • The information in this article has been prepared for general information purposes only and is not intended as legal advice or specific advice to any particular person. Any advice contained in the document is general advice, not intended as legal advice or professional advice and does not take into account any person’s particular circumstances. Before acting on anything based on this advice you should consider its appropriateness to you, having regard to your objectives and needs.

    Insurance products (excluding Travel Insurance) are issued by RACQ Insurance Limited ABN 50 009 704 152 (RACQ). Conditions, limits and exclusions apply. This is general advice only and may not be right for you. This information does not take your personal objectives, circumstances or needs into account. Read the Product Disclosure Statement (PDS) and any applicable Supplementary PDS before making a purchase decision on this product. You can also access our Target Market Determinations on this website.

    Banking and loan products issued by Members Banking Group Limited ABN 83 087 651 054 AFSL/Australian credit licence 241195 trading as RACQ Bank. Terms, conditions, fees, charges and lending policies apply. This is general advice only and may not be right for you. This information does not take your personal objectives, circumstances or needs into account. Read the disclosure documents for your selected product or service, including the Financial Services Guide and the Terms and Conditions, and consider if appropriate for you before deciding.

    Except for RACQ Bank, any RACQ entity referred to on this page is not an authorised deposit-taking institution for the purposes of the Banking Act 1959 (Cth). That entity’s obligations do not represent deposits or other liabilities of RACQ Bank. RACQ Bank does not guarantee or otherwise provide assurance in respect of the obligations of that entity, unless noted otherwise.

    RACQ Operations Pty Ltd (ABN 80 009 663 414 AR 000234978) and Members Travel Group Pty Ltd (ABN 45 144 538 803 AR 000432492) are acting as an Authorised Representative of the issuer of the insurance, Tokio Marine & Nichido Fire Insurance Co., Ltd. (ABN 80 000 438 291 AFSL 246 548). Any advice set out above is general in nature only, and does not take into account your objectives, financial situation or needs. Before purchasing any travel products, please consider the RACQ Travel Insurance Product Disclosure Statement (PDS) and the Target Market Determinations (TMDs) that apply to these products. Whilst the PDS outlines the Terms and Conditions of these products, the TMDs outline the intended class of customers that comprise the target market for these travel products. This will allow you to consider which products best suit your objectives, financial situation and needs and consider the products appropriateness to your personal circumstances. TMDs also outline matters involving the distribution and the review of these products. The PDS, Supplementary PDS and TMDs for each travel product can be found here.