RACV chief engineer Michael Case said there was no logical reason for the huge differences.

“If the smaller outlets can drop their prices why can’t the larger service stations?” he told The Standard.

“It’s a pattern we are seeing across other regional centres — high charges cannot be justified.

“Wholesale fuel prices are at their lowest in four years.”

The official refinery terminal gate price in Melbourne this week was 112 and 113 cents a litre for unleaded petrol, but in Warrnambool yesterday it was selling between 132.9 and 135.9 cents a litre without shopper docket discounts.

At Warrnambool Cheese and Butter’s fuel outlet in Allansford it was 123c/l, as it has been for at least a week, while Nullawarre general store was slightly cheaper at 122.9 cents — just above Geelong’s 121.8c.

Colac was among the state’s highest at 141c/l, just below Horsham’s 143.3c, while Portland’s prices dropped to 136c.

However, the disparity between diesel prices is not so pronounced. 

It sells for 128.9 cents a litre at Nullawarre, making it one of the cheapest outlets in the state, while at Warrnambool it was selling for upwards of 134.9 cents a litre and in Melbourne many outlets were selling at 132.9c/l. 

Figures from the Australia Institute of Petroleum show the national average Australian petrol price this week was at 128.4 cents a litre and the national average wholesale price was 114.4 cents a litre.

However, the national average difference between wholesale and retail prices has risen from 9.8 cents a litre in January to 14c/l now as retailers gouge out higher profits.

Wholesale prices are tipped to fall even further in the next week or so.

Given that the industry uses a freight cost from refinery terminal to Warrnambool of about 3.5 cents a litre, there has been speculation of collusion between the city’s retailers, but Mr Case said that would be hard to prove.

He said motorists could apply pressure on outlets by shopping around.

“A lot of people will be on the move for summer holidays and they can plan ahead by checking on our website for fuel prices and stop accordingly to fill up where it’s  cheapest,” he said.

“There’s been a rapid decline in world oil prices in the past few months and no sign of an increase soon.”

Nullawarre store operator Ashley McDowall said sales had been steady, but were likely to increase with the holiday tourism influx.

“We generally try to match the Allansford price,” he said.

“Warrnambool outlets should be a lot cheaper because they have bigger storage tanks. As a family operation we can be a bit more flexible on margins.”