Driver Knowledge Tests

How to choose the right fuel for your car

For most motorists, there are only two choices when it comes to filling up a vehicle: unleaded petrol or diesel. However, while this choice may be true on a very cursory level, there is more to choosing how to fuel up your car than meets the eye. This article will investigate the differences between the different types of fuel and provide you with a succinct overview regarding which may be correct for your motoring needs. 

Determine your car’s octane requirements (if petrol-powered)

Understanding the octane requirement of your car is crucial if you not only want to get the most out of your engine but also if you want to keep it purring along nicely. Using lower-grade gas than your vehicle needs can cause all sorts of issues, including knocking, among other problems. However, you also need to bear in mind that going for a grade higher than required doesn’t necessarily mean you will eke out any more performance or fuel economy benefits. In fact, doing so will simply cost you more without any discernible advantages. Although newer cars with sophisticated fuel injection systems can alter ignition timing to some degree to prevent knocking when lower octane fuel is used than recommended, the best practice is still to use the specified grade of fuel as stated by the owner’s manual. 

But if you’re reading this post, chances are that you have read that entire paragraph and are still none the wiser regarding what octanes are, so let’s remedy that and take a look at the two main options typically on offer at larger petrol stations.

Regular (91 octane)

For most vehicles in today’s market, 91 octane, which is generally referred to as “regular,” will provide you with sufficient power for normal driving around town and on the highway without any issues. While some countries have lower octanes (down to 87 in some cases), 91-octane is considered the benchmark in Australia and New Zealand due to its higher resistance to engine knocking and is perfectly adequate for most people’s needs. 

Premium (95 or 98 octane)

If you are fortunate enough to own a high-performance car and want to get the most from the power unit under the bonnet, you will need to up your game (and dig deeper into your wallet) and upgrade to whether 95 or 98. While the steeper cost of 95 or 98 RON may be hard to swallow at the pump, drivers of high-performance machinery demanding a premium diet will experience the intended power output and responsiveness only with the recommended high-RON fuel. This is because cars designed to run optimally on these higher RONs allow for more aggressive tuning and heavier loads that all contribute to a far more enthralling experience when behind the wheel. 


Most diesel in petrol stations is a form called 2D. This is good for warmer climates. Sometimes 2D is mixed with 1D, which makes it better for cooler climates. In really cold climates, 1D might be the only type of diesel offered. You won’t know this at the pump, though – it’ll just be called diesel.


Some fuels come with additives to help clean your engine of deposits. These are proprietary to the manufacturer.

Some older vehicles that only ran on leaded petrol may need an additive every time you fill up because unleaded petrol doesn’t have the lubrication that lead provides for these types of engines.


Some fuels are mixes of biofuels and will be named with a number that represents the percentage of biofuel, e.g. E10 has 10% ethanol. Newer vehicles can usually run on biofuels.


Some older vehicles still run on LPG or liquified petroleum gas, but this is much less common now. Sometimes this is called propane, LP Gas or AutoGas.

Check your car’s owner’s manual if in doubt

If you are still in the dark and simply need to know what kind of fuel your car takes, you can always fall back on the trusty owner’s manual, which will clearly state the type and RON that your model takes. It’s worth taking some time to read it through, and although it may be pretty dry reading, you will learn about what fuel it takes, along with a plethora of other valuable information that will help you when it comes to basic maintenance and upkeep.

Filing up your car isn’t quite as simple as it first appears as you have read. However, by ensuring you use the correct fuel, you will either save money by not wasting it on overkill octanes or increase performance if you happen to have a high-powered motor.

Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists

Posted in Advice