Petrol prices are notorious for fluctuating wildly in the lead up to a long weekend. The "official" explanation is tied into the economics of supply and demand - but we all know price gouging plays a part too. (Citation needed.)

Fortunately, it's possible to predict when to avoid the bowser and when to fill up your tank by engaging in a little market research. The math boffins at comparethemarket.com.au have done the hard work for us. Here's a petrol cheat sheet for Australia's major cities this Labour Day weekend.