Motorists can breathe a sigh of relief with economists predicting the cost of fuel to drop to its lowest in 18 months.

Falling global oil prices and a buoyant Australian dollar are the main factors prompting the expected price drop to $1.20.

Commsec economist Savanth Sebastian said the fall could be just the start of the savings.

“Over the next month or so I think we will see prices get potentially below that point,” he told Seven News.

But Chris West from the Royal Automobile Association of South Australia (RAA) told Seven News retailers are unlikely to pass on the full savings to motorists.

“Retailers continue to drag their feet,” he said.

“They’re absorbing savings and pocketing them instead of passing onto motorists.