SA motorists hit by spike at the bowser

South Australian motorists are being urged to fill their tanks today or pay more at the pump, as petrol prices rise for the first time since November.

Many petrol retailers across Adelaide have increased their prices to more than 116c a litre - a jump of more than 10c - since late Saturday.

RAA senior analyst Chris West said petrol stations began hiking prices yesterday morning and he expected most to follow by the end of today.

"Given how quickly the price has transitioned, it could be just 48 hours for prices to transfer from the lowest price to the highest price," he said.

Adelaide had experienced a low price fuel cycle for more than two months

He said he expected about 75 per cent of retailers to reach the price peak by the end of today and prices may remain high until after Australia Day, next Monday, January 26.

"There might be a retailer that will buck the trend and try to undercut the competition - we hope there will be - but they may be hard to find," he said.

"It is not a good picture. The best people can do is get out and fill up before the majority of retailers have shifted." Mr West said Adelaide had experienced a low price fuel cycle for more than two months.

"A lot of people haven't seen a spike since November 13. It's been a long, long time and motorists have been enjoying good prices," he said.

"We were aware of a possible rise and it's happening. The spike appears to be happening at different points across the city.

"Retailers are trying to push the prices higher." Mr West said some service stations across the city raised prices as early as 8am yesterday and it was only a matter of time before the rest followed.

The last peak was at 149c a litre in November last year

On Saturday, the average daily price for unleaded petrol in Adelaide was 105c a litre - a low not seen since January 2009. The last peak was at 149c a litre in November last year.

Petrol prices have been falling for the past 60 days, pushing the discounting cycle out to what the RAA says is a record.

The prices were being kept down by a combination of falling crude oil costs due to low global demand, and a marketing battle involving new retailer Costco in Adelaide, the RAA said.

MotorMouth managing director Alan Cadd said Adelaide petrol retailers could not sustain the low price and it was inevitable it would rise again. "We have been saying that this is likely to happen at some point, we just don't know when and we hope motorists have heeded our advice to keep their tanks full ... Motorists that have not topped up, do so as soon as possible."