"That means fuel companies have not passed all of the lower costs onto motorists, although some service stations have discounted prices below $2 a litre."
Compared to a year ago, motorists buying 40 litres of petrol today would be saving about $6, he said. That equated to about $158 a year for a typical two-litre car.
"International fuel prices have been consistently falling due to lower global demand, and increased supply as refinery production comes back after shutting down for maintenance," Stockdale said.
In April, some Gull stations were offering 91 octane for $1.94 a litre at manned stations and $1.90 a litre at unmanned stations.
Stockdale said although some stations had been offering 91 below $2, that had not been widespread yet.
"Some service stations have dropped below that mark but it's not consistent. Some are above and some are below."
He predicted sub-$2 prices could soon be the norm.
"Although in the last few days oil prices have risen slightly, at current trends there is a good chance the price of 91 octane petrol will fall below $2 a litre soon, the first time since June and July last year."