Perhaps no one in the country knows more about gas prices than Dan McTeague.

He’s been watching them for 30 years and founded Gas Wizard, a website that helps drivers find the lowest prices near them. With the national average now above $1.90 a litre, he says people are hungry for ways to save this long weekend. He has one piece of advice that still surprises many of them.

Never buy gas before 6 p.m.

“Anyone who takes advantage of that is going to wind up with a few extra bucks in their jeans,” McTeague said.

He’s noticed a consistent pattern: prices at many Canadian gas stations drop in the late afternoon and into the evening — anywhere from three to seven eight cents a litre. It doesn’t happen at every station, but McTeague says it happens at most.

The exception is Atlantic Canada, where prices are regulated.

The reason comes down to margins. He says gas stations control only about 12 cents per litre on fuel and the rest is crude oil costs, refining costs and taxes.

“That’s their profit retail margin,” he said. “And usually, by mid to end of day, they’ve covered what they need to cover.”

Once they’ve hit that threshold, station owners are willing to trim prices to drive traffic because the real money isn’t necessarily at the pump: it’s in the merchandise sold inside.

“I saw the other day a can of Canada Dry ginger ale selling for $3.99,” McTeague said. “The money is in food. It’s in donuts. It’s in coffee.”

If cheap gas gets you in the door, McTeague says convenience store attached to the gas station makes up the difference.

Stations also benefit from volume. Moving more fuel because of a cheaper price can earn them better rates from their supplier on the next order.

“It’s almost like clockwork,” he said. “Most gas stations, not all, but most will drop their retail margins after 6 p.m. And the price goes right back up at midnight.”

He says the pattern holds in cities including Vancouver, Toronto, Ottawa, Montreal and Quebec City.

Weekends can be even better. McTeague says Sunday night after 6 p.m. is probably the best time of the week to fill up, sometimes shaving off an extra few cents a litre compared to weekday evenings.

His own wife started following the advice a few years ago after they talked it over.

“She’s figured out that we’ve saved close to $500 a year on two vehicles. So, $250 a vehicle,” he said.

“It’s the tried and true.”