Is gas really cheaper on Tuesday? Where it is, and where it isn't

The short answer

"Fill up on Tuesday" is advice from a market with a regular price cycle, moved to markets that may not have one. Where prices cycle, the cheap moment is the day before the next jump, and that day is not fixed. Where they don't cycle, the weekday is a small effect next to wholesale prices, the station you pick and how much you buy.

Toronto: a weekly cycle, but not a fixed day

The best-known Canadian study is Michael Noel's, published in The Journal of Industrial Economics in 2007. He recorded prices twice a day at 22 Toronto stations for 131 consecutive days, from February 12 to June 22, 2001. Each station raised its price "by the full height of the cycle in a single jump," then cut it "in small amounts over four to ten days." The typical cycle lasted about 13.8 half-days, "or about a week," and the typical jump was about 5.6 cents a litre before tax. The wholesale (rack) price didn't cycle; the pattern came from how stations competed.

Two details matter for anyone looking for a cheap day:

• The jump moved. Noel writes that "the price increase occurs on a different day of the week from one week to the next," and that single cycles ran from 4 to 10 days.
• Tuesday was the most common day for the jump, not the dip. Of all the price jumps he recorded, 37% came on a Tuesday, 22% on Monday, 21% on Wednesday, 13% on Thursday, 6% on Friday and 1% on weekends.

So in that data, "buy on Tuesday" would often have meant buying on the day prices went up. The data are from 2001 and from one city; we haven't found a newer study with the same station-level detail for Toronto, so we can't say whether the pattern still holds.

Australia: cycles of one to six and a half weeks

Australia's competition regulator, the ACCC, tracks price cycles in its five largest cities. In 2025 it measured average cycles of "5 weeks in Sydney, 6 weeks in Melbourne, 6 and a half weeks in Brisbane, 2 and a half weeks in Adelaide, 1 week in Perth." It says cycles "don't occur in the smaller cities or in most regional locations," and gives no buying tips for Canberra, Hobart or Darwin.

Its advice is about where a city is in its cycle, not the weekday. When Perth prices "appear to be around the lowest point of the cycle," it says "now is a good time for motorists to buy petrol"; when prices have gone up, it suggests shopping around for lower-priced retailers. A cheapest weekday can't exist in a city whose cycle is five or six weeks long.

Metro Vancouver: wholesale and supply first

We haven't found a published study showing a regular weekly price cycle in Metro Vancouver. Consumer price-tracking sites describe at most a mild day-of-week rhythm, with wholesale and supply news moving prices more. They don't publish their methods, so we don't quote their numbers.

What is on the record is how much supply matters. In its 2019 inquiry, the BC Utilities Commission found "a significant unexplained difference" of about 13 cents a litre between wholesale gasoline prices in Southern BC and its Pacific Northwest comparison; after public comments, its supplementary report put the gap at 10 to 13 cents. It also said "the cost of the most expensive 5% of supply in the Pacific Northwest is driving the price of all gasoline sold in BC." A price set by wholesale supply like that doesn't wait for a particular weekday (our reading).

Why weekday advice travels badly

• Cycles differ by city. Noel notes that in other cities cycles have lasted "several weeks or even several months," and some markets have none. A rule learned in one city says nothing about the next.
• The cheap day is a phase, not a date. Even a weekly cycle drifts, as Toronto's did.
• Most public data can't show it. Ontario's Fuels Price Survey, the deepest Canadian series, goes back to January 3, 1990 but is published weekly, for 10 markets. A price taken once a week can't reveal a cycle that lasts a week. Noel makes the same point about weekly averages hiding the shape of the cycle.

What actually saves money

• Don't run to empty. With a quarter tank left, you can wait a day or two for a better price. With the light on, you buy wherever you are, at whatever point in the cycle (our reasoning).
• Count the detour. A station 3 km off your route adds about 6 km. At 9 L/100 km that burns about 0.54 L, or 97 cents at $1.80 a litre. A 3-cent saving on 40 L is $1.20, so the detour leaves you 23 cents ahead, before your time (our arithmetic).
• Think in ranges. Any forecast of tomorrow's price is a range. If the range is wider than the weekday difference, the weekday tells you nothing.
• Watch your usual station. The gap between two stations you already pass can be steadier than any weekday effect (our observation).