Here's our handy guide:
The most commonly sold fuels are unleaded - unleaded (ULP), premium unleaded (PULP) and ultra premium unleaded (UPULP) - all of which have a RON (Research Octane Number) rating, which determines the petrol's resistance to pre-ignition. Vehicles filled with fuel that has an insufficient octane rating for the model make a characteristic ‘knocking' sound, which means the fuel is detonating instead of burning smoothly. This is a waste of energy and can even damage the engine, so it's important to make sure you choose the fuel with the recommended RON rating for your vehicle.
ULP is 91 RON and suits most Japanese and locally built vehicles, as well as some pre-1986 cars, including the KC Laser and Mazda 323. PULP has a 95 or 96 RON rating and is used to run European cars, as it is the standard octane there. Vehicles such as the Subaru WRX STi, plus some Porsches and high-powered Mercedes and BMWs are optimised for 98 RON or UPULP. They can run on lower octane fuels but their power is reduced.
Though Lead Replacement Petrol (LRP) is no longer available at the pump, some pre-1986 vehicles, such as Kingswoods and early Falcons, still need it. Their drivers have to buy an additive and mix it with PULP themselves to get the required 97 octane rating.
Liquified Petroleum Gas (LPG) is made from butane and propane and costs less than petrol. It is used by models such as the Ford Falcon, which are factory fitted for LPG, and ‘bi-fuel' vehicles, which have a petrol as well as an LPG systems.
If you have a fleet car, the chances are it is running on diesel, which is also used for some 4WD, heavy and commercial vehicles.
Shell has recently begun selling a 100 RON premium fuel with 5 per cent ethanol, an alcohol fuel alternative produced from crops. The excise on this fuel is subsidised until 2011, but it isn't suitable for use in some older vehicles. As in all cases, check your model's handbook or with the manufacturer to make sure you're using the correct fuel for your vehicle.