Most common petrol myths, busted

E10 fuel is regular unleaded petrol that's blended with 9-10 per cent ethanol. It's usually the cheapest option at petrol stations. But E10 fuel tends to get a bad rap, with some Australians believing that it can cause problems with your car.

That might have been true when E10 fuels were introduced about 20 years ago, when older cars' engines would get dirty and cause issues with ethanol fuel. Nowadays, though, technology advances have ensured that most vehicles can safely use E10 fuel. In fact, many cars on Australian roads are designed in Europe and Asia, where there is a large ethanol usage.

You can check if your car is compatible with E10 fuel on the inside of your fuel filler flap, which should list the lowest-grade fuel you can use in the car (anything higher-grade is also fine), or on the manufacturer's website.

This myth is another holdover from several decades ago, when older vehicles could have water or contaminants stuck at the bottom of their fuel tank. But in modern cars, petrol is pumped from the lowest point in the fuel tank, so whether your car's tank is full or empty makes no difference to the petol quality.

It's true that country petrol prices are often higher than in the city, but not always.

Regional fuel retailers generally sell less fuel than metropolitan retailers, while transporting the fuel large distances into regional areas can be quite expensive. As a result, country petrol prices generally remain pretty steady.

That said, regional prices do drop below Melbourne prices on occasion. There are times when Melbourne’s price peaks are substantially higher than regional prices. Regional drivers coming to Melbourne should always check city prices to see if it’s cheaper to fill up at home.

The days of predicting the cheapest petrol day are gone. In the past, the price cycle was exactly a week long and everyone discovered “cheap Tuesdays”. But since 2013, the price cycle has varied from nine days to up to two months. It's no longer possible to predict the peak-to-low petrol price cycle and which day fuel will be the cheapest.

"Drivers can use RACV’s fuel price monitor on the free arevo app to find the cheapest petrol prices near them," says RACV Head of Policy James Williams. "The interactive map – which you can sort by distance, lowest price or preferred brand – updates every 15 minutes for accurate pricing."

Petrol stations do sometimes sell below wholesale prices to match or beat their competition. Drivers who shop around put pressure on retailers who want to keep customers. This competition triggers the slow discounting cycle, where retailers reduce the price by one to two cents a day until they get to or below the wholesale price. Often the super-low price lasts only a short time and the price spikes upward again.

The retail price may also be lower than the wholesale price due to the fuel supply chain and the delay between leaving the terminal gate and selling that fuel at the pump.

Manual cars used to be more economical than automatic vehicles, but not any more. When automatic transmissions were new (and quite basic), they typically increased fuel consumption and reduced performance compared to a manual driver who shifted gears efficiently. But modern automatic transmissions can match or better a manual’s economics, as technology like electronic shift control systems now outstrip the average driver's ability with a clutch and stick shift.