Diesel will set a price record for the fourth day in a row when it averages 214.3c a litre across Perth on Saturday, which comes amid warnings unleaded petrol will climb as high as $2.40 by mid-March.

While the average cost of unleaded will drop to 210.9c per litre today, the Motor Trade Association of WA cautioned the top of the next two-weekly price cycle — which falls on March 23 – was likely to bring even greater pain for motorists.

That is because the terminal gate price of unleaded — what retailers pay when purchasing petrol in bulk — continues to surge upwards.

WA’s terminal gate price, which fluctuates in line with the global oil market, jumped from 178.8c per litre on Monday to 196.4c per litre on Friday.

Perth’s fortnightly price cycle is now on a downward trend, meaning motorists can expect to be temporarily shielded from further increases to the wholesale price — but only until the next peak later this month.

“Petrol stations are always running about two weeks behind (in their pricing), which is why we’re saying expect $2.30 to $2.40 within the next few weeks,” MTAWA chief executive Stephen Moir said.

“During the cheap days of the cycle, petrol is often being sold at a loss of upwards of 5c per litre.

“But then of course on Wednesday you saw retailers go to 20c above the wholesale price — so the margins fluctuate.”

The cheapest days in the current price cycle fall on Monday, March 21 and Tuesday, March 22 before another big spike likely to again shatter records on March 23.

The last peak of the fortnightly cycle fell on Wednesday, when unleaded petrol in Perth averaged 208.8c per litre — with individual outlets charging as much as 228.9c per litre.

Figures compiled by the RAC found that if petrol were to average $2.20 per litre across 2022, the average motorist would be forced to shell out an additional $908 to keep their car on the road.

That increases to an eye-watering $1150 extra if petrol were to average $2.40 per litre.

Meanwhile diesel — which rises and falls daily with far less volatility — continues to climb steadily, setting new records every day since Wednesday.

The most expensive diesel in Perth will cost 229.9c per litre on Saturday, compared to 219.9c per litre for unleaded petrol

Diesel is the primary fuel for trucks carting goods across WA and Australia with freight companies already warning they have no choice but to pass on their increasing costs — meaning higher prices for everything from fresh produce to electronic goods.

Whether petrol remains at historically high prices will depend on fallout from the ongoing conflict between Russia and Ukraine, which was resulted in US and UK bans on the import of Russian oil.

Brent crude briefly reached $US130 per barrel earlier this week before dropping back to US$110 on Friday.