WA motorists are being advised to fill their tanks today before petrol stations begin hiking their prices.
FuelWatch says most BP stations and some Caltex stations are expected to start the increase today by raising prices to about 130 cents per litre, with other stations expected to follow suit over the coming days.
The hike by BP is 17.4 cents per litre, while Caltex is increasing prices by 19 cents per litre.
"The difference between the cheapest and most expensive sites is 21 cents per litre, which equates to over $11 filling up the standard 55-litre tank," Deputy Prices Commissioner Aaron Rayner said.
"Over the past three months, Peak and Gull have, on average, been the cheapest brands in Perth."
196 petrol stations will be selling below the metropolitan average of 114 cents per litre, with 60 selling below 109.
FuelWatch recommends buying fuel on Mondays and Tuesdays, when it is generally cheaper than later in the week.