Fuel Types Explained

What different types of fuel are available and which one should you be using? Let's untangle the complexities below:

Replenishing your car with fuel sounds easy – and, with experience, it is – but if you're a new driver, the multitude of different fuel types at the service station forecourt can be more than a little intimidating.

It's not just new drivers who can be overwhelmed. Perhaps you've just bought a new car, wish to herald the coming spring by hiring a car for a school holiday road trip, or are otherwise unfamiliar with exactly which fuel you should be pumping.

FUEL TYPES

At the most basic level, Australian cars run on either unleaded (or ULP), diesel or liquid petroleum gas (LPG). However the consumer plot is thickened by different 'grades' of fuel within those categories.

UNDERSTANDING THE GRADES

LPG is simple – there's just one grade. Diesel, however, is offered in two grades ('regular' or 'premium'). In the case of ULP, you've got 'regular' (91 RON), two grades of 'premium' (95 RON and 98 RON) and ethanol blends (E10) to grapple with.

What do all the numbers mean?

RON stands for 'Research Octane Number', which tells you how much the fuel can be compressed before it spontaneously ignites. In the case of ethanol blends, the numbers also refers to the percentage of ethanol blended into the ULP.

Why is this stuff important?

Engines are not only designed to burn a basic type of fuel but, increasingly, a certain grade as well. While feeding an engine the wrong type of fuel – say, petrol instead of diesel or vice-versa – has always been something to avoid due to the risk of serious engine and fuel-system damage, even running the wrong grade can cause issues. Using a lower RON unleaded than recommended, for example, can lead to pre-ignition or 'pinging'. This is when fuel ignites too early and it can lead to serious engine damage.

CHOOSING THE RIGHT FUEL

Still confused? Well, don't be; feeding your car the right fuel is dead simple – just pop the fuel flap and follow the manufacturer's recommendation printed inside. If your car doesn't tell you its preferred tipple/s here, you'll find it in the owner's manual. If there are no instructions, that generally means the lowest grade of unleaded or diesel will be fine to use.

While running a lower grade ULP than recommended can be bad news, there's really no downside to going higher aside from cost. To work around the higher cost point, work toward occasionally filling up with premium fuel. Typically, filling up with premium fuel on the second to third fill can still reap the benefits of flushing out and cleaning the engine (premium fuels typically contain additives to help keep the fuel system clean). This is the perfect balance between premium fuel and cost.

Diesel is a little different too. Unlike ULP, there's no inherent difference between the combustion qualities of 'regular' or 'premium' blends, so you won't damage a diesel engine choosing the regular grade. But you will miss out on the cleaning and other benefits that differentiate 'premium' fuels.