Adelaide petrol prices were the lowest in the nation during the first three months of this year and buyers in the city’s inner north got the best of the deals.

But retailers are now beginning to line their pockets by maintaining prices at the spike of the fuel cycle for longer.

The RAA’s latest quarterly petrol study shows the average price for unleaded petrol in Adelaide from January to March was 116.5c a litre, compared with 117.1c a litre in Melbourne and 118.8c a litre in Sydney.

In Perth – the city most similar to Adelaide in terms of population and number of service stations – the average price for unleaded petrol was 120.8c a litre, while Brisbane was the most expensive at 121.3c a litre.

The average price for unleaded petrol in Adelaide on Monday was 134.9c a litre. It spiked at 135.9c a litre almost two weeks ago.

RAA senior analyst Chris West said motorists were rewarded with cheap fuel earlier this year because of a change in Adelaide’s fuel cycle, which maintained lower prices for longer.

The RAA study also showed Costco Kilburn topped the list for the cheapest unleaded petrol in the metropolitan area.

Mr West said the introduction of the international discount retailer had prompted strong competition from service stations in the surrounding inner northern suburbs.

Mr West said smaller independent retailers had been active in undercutting prices and keeping bigger competitors honest.

Adelaide Metro Petrol Prices January 1 – March 31, 2015

Average cheapest petrol by band  

1. United Petroleum
2. Woolworths
3. Liberty
4. Caltex
5. Mogas
6. On The Run

Average cheapest petrol by station

1. Costco Kilburn – 404 Churchill Road, Kilburn
2. Caltex/Woolworths Blair Athol – 355 Prospect Road, Blair Athol
3. United Blair Athol – 355 Prospect Road, Blair Athol
4. Ezy Fuel SA Klemzig – 25 O.G. Road, Klemzig
5. Caltex/Woolworths Felixstow – 469 Payneham Road, Felixstow
6. Liberty Windsor Gardens – 386 North East Road, Windsor Gardens
7. Caltex/Woolworths Gilles Plains – 575 North East Road, Gilles Plains
8. Caltex Star Mart Campbelltown – 542 Lower North East Road, Campbelltown
9. BP On The Run Kilburn – 427 Churchill Road, Kilburn
10. Caltex/Woolworths Marryatville – 220 Kensington Road, MarryatvilleSource: RAA, MotorMouth

Extracted in full from Cars Guide.