What's the best day to buy gas in Quebec? We ran the numbers

Ask around for the best day to buy gas and you'll get a different answer from everyone. To settle it, we used the most solid source available in Quebec: the average posted price of regular gas that Quebec's Régie de l'énergie publishes every business day for about a hundred cities and regional municipalities. Here's what those numbers show, and what they don't.

What we measured, and how

We downloaded the Régie's official files for 2023, 2024, 2025 and 2026. They run from January 3, 2023 to August 31, 2026, Monday to Friday only: the Régie publishes nothing for Saturdays and Sundays.

For every complete week (all five business days present, which leaves out weeks with a statutory holiday), we compared each day's price with that week's own average. This cancels out the overall price level: whether a week was expensive or cheap, only the gaps between its days count. That gives 161 weeks per city, from January 9, 2023 to August 28, 2026.

One detail matters: for most of that period, these prices were sent to the Régie by wholesalers and retail networks, usually before 9 a.m. So the "Wednesday price" is mostly a Wednesday morning price. The Régie says its publications now come from its Régie essence Québec database, which stations feed themselves.

The best day to buy gas, city by city

The table shows the cheapest and most expensive day on average in each city, and what the gap between them is worth on a 50-litre fill-up.

Put simply: outside the Montreal area, the start of the week is slightly cheaper than the middle. In Montreal, Laval and Longueuil, no day stands out: every day stays within 0.2¢/L of its week's average.

Why Wednesday is often pricier

The data shows where the increases hide. In Gatineau, right across the river from Ottawa, the average price jumped by 3¢ or more between Tuesday morning and Wednesday morning 50 times out of 183, compared with 27 times between Monday and Tuesday. Saguenay looks the same (47 times) and Quebec City shows a milder version (24 times). The rest of the week, prices drift down, and weekends often push them lower: in Gatineau, Monday morning comes in 1.6¢ below Friday morning on average.

That's how price cycles work: a big jump all at once, then a slow slide, station by station. Our article on why gas prices change so much explains the mechanics.

In Montreal, increases also come in waves, just not on a set day. Friday to Monday has the most of them (21 jumps of 3¢ or more over 170 weekends), but they also show up from Tuesday to Wednesday (13), Wednesday to Thursday (7) and Thursday to Friday (10). On average, it all cancels out.

What day is gas cheapest? On average, not every week

Averages can mislead. In Gatineau, where the effect is strongest, Monday was cheaper than Wednesday in only 89 of 161 weeks, barely more than half the time. In Quebec City it was 71 of 161: less than half, even though the average favours Monday.

Why? In many weeks, prices ease down from Monday to Friday, so Wednesday ends up cheaper than Monday: that happened in 84 of 161 weeks in Quebec City. A handful of big Tuesday increases is enough to pull Wednesday's average up.

In 2026, the pattern got stronger in some cities. Over the 32 complete weeks from January to August, the average gap between the cheapest and priciest day reached 5.6¢/L in Gatineau (about $2.80 on 50 L) and 4.5¢/L in Saguenay, versus 0.7¢/L in Montreal. That's eight months of data: no guarantee it lasts.

To keep those numbers in perspective: on Monday, October 5, 2026 at 8:10 a.m., regular gas cost anywhere from 192.9 to 208.9¢/L depending on the station in Montreal, and from 183.9 to 199.9¢/L in Quebec City, based on prices reported to the Régie. That's a 16¢/L spread, or $8 on a 50-litre fill-up. Picking the station matters far more than picking the day. Our article on Quebec gas prices from the Régie de l'énergie breaks those gaps down city by city.

What time do gas prices change? What Gazo sees

The Régie's averages say nothing about weekends or time of day. Since Saturday, October 3, 2026, Gazo has logged every price change in the Régie's official feed. It's a very short window with some gaps, so treat it as a glimpse, not a rule. Still, what we saw is telling.

• Saturday night, Montreal area: between 9:35 and 10 p.m., about ten stations raise regular by 5 to 15¢. Between 10 p.m. and 12:45 a.m., more than 300 stations follow, with a median increase of 12¢.
• Sunday, 7 a.m. to 8 p.m.: Gazo logs 1,699 price drops across Quebec, 1,385 of them between 1 and 4¢: the slow slide after the jump.
• Sunday night, another wave: between 7:30 p.m. and 12:15 a.m. (Gazo has no reading in between), 374 stations raise regular. In the Montreal area, Gazo counts 341 of them in the wave, spotted at 12:18 a.m., and the median price goes from 194.9 to 204.9¢/L.

Two increases on two weekend nights don't make a rule. They do show that a hike can land on a Saturday night, and that the Régie's Monday figure already includes it. A few more weeks of logging will tell us more.

The best time to fill up

If you remember one thing: the best time to buy gas is when you need it and you've compared the stations around you. A few habits that beat any lucky day:

• Compare when you fill up. In Quebec, every station reports its prices to the Régie, and Gazo reads that feed every 2 minutes. The list sorts by price, and no station pays for a better spot. City pages such as gas prices in Montreal, Quebec City or Gatineau show current prices.
• Watch for the "Prices are going up" banner. When a wave of increases starts in Quebec, Gazo shows it for free, along with nearby stations still at the old price and a "Go" button that opens Google Maps, Waze or Apple Maps.
• Check tomorrow's trend when there is one. In some Quebec cities, Gazo shows a forecast for the next day only if it was right at least 65% of the time over 30 days. Otherwise, the app says so plainly: "No clear trend". In the Montreal area, where increases show no warning signs in the daily averages, the banner is your best heads-up.
• Don't wait for the warning light. Once it's on, you stop at the first station you see. Fill up around a quarter tank and you get to choose.

Driving in Ontario, the West or the Maritimes? The Régie calls its station-by-station price map a first in Canada, so outside Quebec Gazo relies on prices reported by drivers, plus an official area estimate when none are recent. Comparing before you fill up works the same way.

Gazo+ ($2.99 a month or $19.99 a year) adds price alerts and a 30-day price history for every Quebec station, handy to tell whether your usual station is on the high or low side lately. And to spend less on every fill-up, our 12 ways to use less gas often do more than any calendar.