Adelaide motorists paying four-year high petrol prices

Adelaide motorists are being slugged more than $1.60 per litre for unleaded petrol in a price surge experts say shows no signs of easing.

The cost of fuel has soared to its highest level in around four years, with some outlets charging drivers $1.63 per litre.

South Australia's peak motoring body, the Royal Automobile Association (RAA), is urging motorists to avoid the major retailers and to fill up at or below $1.36 per litre.

"Independents are important to keep the price of fuel down," Mark Borlace from the RAA said

"They're often the last ones to go up in price and they're often the first ones to try and bring the price down.

The spike in the wholesale cost is being blamed on increasing oil prices in the Middle East, which are showing no signs of slowing down.

"There is some pressure because of what's happening in the world for the price of fuel to continue to rise for a while, but certainly doesn't account for the 30 cent spikes we're seeing," Mr Borlace said.

"$1.63 per litre looks like it's the top of the market right now - we hope it wouldn't go higher."