Everyone wants to get the most out of their car, and it is because of this that rumours about how to save petrol abound. And while most people (we hope!) have by now realised that such additions as "speed holes" or painting your car red will not make it more fuel efficient or faster, there are still a few myths out there that, we feel, are best busted. When you're organising your car rental in Melbourne, Sydney or Brisbane, be sure to keep these tips in mind.

You don't (necessarily) have to fill 'er up in the morning

It's not true that filling your tank in the morning will give you more gas for your greenback. According to Consumer Reports Online, the story goes that cooler morning temperatures equal cooler, and therefore more dense, gasoline. However, the majority of gas stations keep their stores of petrol underground – and the temperature does change much down there. So, fill 'er up whenever you like!

Don't be idling

Some say that turning your engine off and then restarting it when, say, you pull over to answer your cellphone will burn more petrol than simply letting the motor run idle. The California Energy Commission's Consumer Energy Centre has debunked this. They state: "The bottom line is that more than ten seconds of idling uses more fuel than restarting the engine."

You can leave those windows open

Another popular theory is that having your windows open affects the aerodynamics of your car to such an extent that, at high speeds, it will cost you extra fuel when driving. Consumer Reports Online actually tested this one out, measuring how much petrol a car driving at 65 miles per hour (about 105 kilometres per hour) used up over a certain period of time with and without the windows open. Turns out it doesn't make any difference.