It's a question that's been asked almost since Henry Ford invented the automobile industry - why are gas prices so high?

The recent cold snap sent demand for oil soaring but that's not the only reason you've suddenly seen the cost of a fill-up soar from 69 cents last month to 90 cents-plus this week.

It's the old law of supply and demand and all of sudden, there's a lot more of the latter than the former. The reason? A fire at a refinery plant near Nanticoke in Southwestern Ontario.

The facility is owned by Imperial Oil, which operates Esso stations in Canada. It was those flames which have added fuel to the fire for those looking for cheap gas. Or maybe that should be taken fuel away.

A CityNews survey shows as many as 20 Esso outlets in the GTA are close to running out of gas.

Most admit the shortage is only temporary, but that won't help you if you pull into one of the affected stations running on empty.

"There are some service stations that will, from time to time, be without product for a few hours in the next 10 days," admits spokesman Robert Theberge.

Some drivers have already begun to notice.

"Actually [this is] the third [Esso] gas station I'm coming to ... and they're running out of gas," explains one unhappy motorist.

"This is my second or third Esso and I just can't wait. The gas light's going to run out," another complains.

"I'm running on empty right now," concedes a third. "So I'm coming out of my way to get gas."

There have been reports that the shortage is having a ricochet effect, driving up prices at other oil company outlets.

But Theberge insists that's not the case.

"Twenty service stations across Ontario without product is not significant enough," he counters. "You are talking about 2,000 service station stations in Ontario to affect price ... It is not enough to affect price."

But that hasn't been the experience in London, Ontario, where some stations have seen major jumps as Esso is forced to shut down empty pumps.

Imperial claims the CN Rail strike is squeezing supplies by keeping its trucks busy and unavailable to haul fuel here. Also causing trouble: the long cold spell, which has delayed shipments from the U.S., as well as production problems at a refinery in Sarnia.

The CN problem may soon be resolved - the federal government is preparing back to work legislation that could see striking conductors return to their jobs.

But it's that fire that took place on Thursday morning that's taken things from bad to worse.

"It's the straw that broke the camel's back," Theberge agrees.

The refinery in question turns out around 118,000 barrels of fuel a day.

So should you rush out and fill-up as quickly as possible in anticipation of an all out shortage?

Theberge says that's the worst thing you can do.

"Consumers should continue with the normal buying pattern," he pleads. "We apologize for those that are buying at Esso and may end up in a place where there is no product, but the Shell, Petro-Canada or other service stations next door, should have it. The Esso a little further down the road probably has it, too.

"But it would be a tremendous mistake if people went out and started panic buying."

Esso insists its competitors will be able to meet consumer demand until it's back up to speed and that the Minister of Energy is aware of the issue.

But until all those problems are resolved, expect to keep paying through the hose.

It's another day of nervous motorists asking themselves: should I or shouldn't I fill up the car?

It may not even depend on whether you really need gas. A rotating shortage of fuel at some 75 Esso stations across the province - including at least 20 here in the GTA - is leading many to top up their tanks just in case.

We first told you on Tuesday that the stations have been running on empty because of a so-called 'perfect storm' of events.

A fire in a Nanticoke plant has lessened reserves.

The CN Rail strike is tying up tanker trucks which would otherwise be used to bring in shipments from other provinces and the U.S. (That may soon be resolved. To find out how, click here.)

And the bitter cold has driven up demand and prices.

The company is asking customers to excuse the temporary glitch, which they claim should be over by next week. They're telling stations that run out of the precious liquid to sell their premium supplies for the same price as a litre of regular in the meantime until every drop is gone.

And they're actually asking you to visit their competitors if the station you stop at is out completely. You can tell which ones are affected by the "0.00" price on the station marquee.

The one thing they don't want you to do is panic buy elsewhere - deliberately filling up in a mad rush just in case things get worse.

Esso insists the shortage at its stations and some other independents it supplies with gas - including Canadian Tire, which has also been forced to close 10 outlets - simply isn't enough to cause the price to go up.

But many motorists are greeting that news with suspicion and some raised eyebrows.

Prices in the GTA were hovering around the 91-96 cent mark on Wednesday, a huge jump since last month's mild spell brought them down to the low 70s range.

And Imperial Oil is worried that if there's a stampede at the pumps it will create a kind of self-fulfilling prophecy about a shortage that really doesn't exist.

"If people go crazy into panic buying, it could look very ugly by the end of the week," warns spokesman Robert Theberge. "They will put a lot of stress into an already overstressed situation."

But the oil giant is adamant their problem isn't causing the sudden price hikes. Are they right? CityNews.ca decided to investigate by looking at the current prices drivers are paying in other parts of the country.

A weekly survey by industry analyst M.J. Ervin and Associates, taken on Tuesday, shows that Ontario is mostly on par or a just little above most other big cities.

That's small comfort for those who are looking at ever higher prices and even the hint of dwindling reserves.
Here's the list by province, based on a litre of regular.

B.C.
Vancouver: $100.7
Victoria: 99.9

Alberta (no provincial gas tax)
Calgary: 85.2
Edmonton: 85.4

Saskatchewan
Regina: 93.5
Saskatoon: 93.5

Manitoba
Brandon: 88.0
Winnipeg: 88.0

Ontario:
Hamilton: 91.7
Kingston: 86.8
London: 94.3
North Bay: 89.9
Ottawa: 91.3
Peterborough: 85.7
St. Catharines: 89.4
Sault Ste. Marie: 91.7
Sudbury: 87.5
Toronto: 91.5 (now higher in some areas)
Thunder Bay: 96.9
Windsor: 92.3

Quebec
Montreal: 93.3
Quebec City: 95.0
Sherbrooke: 94.4

New Brunswick
Fredericton: 89.5
Moncton: 89.3
Saint John: 89.3

Nova Scotia
Halifax: 94.8
Sydney: 98.9

Price Edward Island
Charlottetown: 95.9

Newfoundland/Labrador
St. John's: $100.4
Gander: $102.9
Corner Brook: 101.1

Northwest Territories:
Whitehorse: 97.6
Yellowknife: 98.8