Motorists expecting the pump price of gasoline to drop as suddenly as the headline cost of crude oil are likely riding for a disappointment.

Many consumers misunderstand the relationship between the price of crude and the retail level of gasoline, says Calgary energy industry consultant Michael Ervin.

Crude oil, the main ingredient in gasoline, continued its slide Thursday, hovering around US$108 per barrel. That is a steep drop from its all-time high of US$147.27 per barrel set July 11.

However, the oil price quoted in daily media reports does not refer to its value at that particular moment, but rather a contract for crude that will be delivered the following month.

"Right off the bat it would be pretty misleading to expect today's pump price to be responding to an October crude oil price,'' Ervin said in an interview Thursday.

"It is linking two events that should not be linked.''

One of the biggest myths is that gasoline prices move up or down by at least as much as crude does, Ervin said.

For instance, a year ago crude oil was quoted at the US$75 a barrel level, and the national average gasoline price compiled by MJ Ervin and Associates was $1.034 per litre.

When oil hit $147, up 96 per cent from early September 2007, gasoline was at $1.40, an increase of 35 per cent.

This week's average pump price is $1.32, slightly higher than a month ago despite crude's pullback.

"It illustrates that there is a very indistinct relationship on the way up,'' Ervin said, "and it's a very indistinct relationship on the way down.''

Gasoline prices are expected to abate this autumn, but largely for reasons other than moves in crude oil, he added.

"In the fall, demand for gasoline starts to diminish and as a result we usually see an easing of the gasoline price even if the crude price doesn't go down,'' he said.

"That's been characteristic of the gasoline market for about as many years as we've tracked the price.''

Eventually, refiners which have bought crude at lower prices will see their costs go down, which will take some more of the edge off gasoline prices, Ervin said.