Petrol prices have fallen to less than a dollar a litre on average for the first time since January 2009.
Adelaide's average price for unleaded petrol was 99.9c a litre yesterday - a price not seen since January 2005, when the average was 97.3c a litre.
Adelaide's average price was also the cheapest in the nation, - lower than the 111.6c a litre Perth price and 2c a litre less than in Sydney.
The cost of filling the tank of a typical family sedan is now $37 less than this time last year.
The fall in oil costs has seen Adelaide's average price plummet from 120.9c a litre last month and 152.9c a litre in January last year. The cost of filling the tank of a typical family sedan is now $37 less than this time last year.
The RAA urges motorists heading off this long weekend to fill up in the city. Unleaded prices per litre in country centres yesterday included Port Augusta 122.2c, Port Lincoln 121.7c, Victor Harbor 114.9c and Clare 113.8c.