TL;DR: Brisbane’s cheapest day of the week is worth under a cent a litre. The price cycle you’re ignoring is worth about 45. You’re arguing over the wrong number.
The day-of-week gap in Brisbane fuel prices is under a cent a litre — and depending on how you measure it, closer to 0.1. The cycle you fill on top of swings around 45 cents a litre. That is the whole post, but the folklore deserves a proper hearing first, because it can’t even agree with itself.
The claim
Everyone knows the cheap day. The trouble is nobody knows the same one.
“cheap tuesday @ brisbane” — ‘issh’, Brisbane, Whirlpool, 2010
“yeh ive found thursday to be the cheapest day in the cycle” — ‘Franco Cozzo’, Whirlpool, 2010
“It might be cheaper on Tuesdays, but it is cheaper on Fridays” — ‘JunkCrusader’, Whirlpool, 2010
Three drivers, three different cheap days, one forum thread. The RACQ traces “Cheap Tuesday” back to the 1970s, when people were paid in cash on a Thursday, filled up on the way home, and stations dropped prices by Tuesday to pull in the drivers who’d run dry. There’s even a named culprit for the Thursday spike:
“You can thank Centrelink payments for the Thursday spike” — ‘affable’, Whirlpool
It’s a tidy story. It’s also fifty years old. So we checked it against every price change Brisbane stations reported over the last seventeen-odd months.
What we checked
The question is narrow and answerable: on an average Monday, Tuesday, Wednesday and so on, do you pay less for the same fuel?
To answer it cleanly you have to remove the cycle first — otherwise a stretch of expensive Wednesdays just tells you the cycle happened to peak midweek during your sample, not that Wednesday is dear. So we took the daily median price across 430-plus Brisbane metro stations, subtracted a rolling baseline to strip the cycle out, and then averaged what was left by day of the week. We ran it for both ULP (regular 91) and E10, and we ran it separately for 2025 and 2026 to see whether the answer held still.
Everything below is the Queensland Government price feed — the actual price each station reported it was charging, not a driver’s guess at the bowser.
What the feed shows
Averaged over the full window, there is a cheapest weekday. It’s Tuesday, by a whisker, and the dearest is Wednesday. Here’s the gap:
- ULP: Tuesday to Wednesday spread of 0.74 c/L
- E10: Tuesday to Wednesday spread of 0.75 c/L
Two different fuels agreeing to within one-hundredth of a cent isn’t a discovery. It’s a tell. When two independent measurements land on the same tiny number, you’re usually looking at an artefact of the method, not a real effect. Tighten the way you remove the cycle and that 0.74 shrinks toward 0.1 c/L, and the “cheapest” day stops being Tuesday at all.
Then there’s the year split, which is where the story falls apart:
- In 2025, Tuesday was the cheapest weekday.
- In 2026, Tuesday was one of the dearest, and the cheapest slot moved to Friday.
A real calendar effect doesn’t reshuffle its own leaderboard year to year. Noise does exactly that. Rank the stations a second way — score each station’s own week and average across all of them — and the cheapest day flips to Friday again, with Tuesday coming out dearest. Two fair ways of counting, two different “cheap days.” That is the signature of no signal.
The verdict
There is no reliable cheap day of the week for petrol in Brisbane. The best case for one is a gap of under a cent that can’t hold its ground across two years or two counting methods.
Now the number that actually moves your bill. Over the same window and the same stations, the typical price cycle swung about 45 c/L from trough to peak inside a single month. Set that beside the day-of-week gap:
- Day of the week: under a cent, and unstable
- The cycle: about 45 c/L, every month, reliably
You are chasing a fraction of a cent while standing on top of a forty-five-cent move. On a 60-litre fill, “the right day” is worth loose change from the console. The right week is worth the better part of thirty dollars.
So what
Stop asking which day. Start asking where you are in the cycle. When Brisbane prices sit in the cheap part of their monthly range, fill up — Tuesday, Sunday, whenever you’re driving past. When they’re in the top of the range, a half-tank to get you through beats a full one at the peak, on any day of the week.
Pinly shows the cycle position on the map so you don’t have to keep a mental scoreboard. That’s the number worth watching.
One honest limit. This measures the price you pay on a given weekday — which is what “cheap Tuesday” plainly claims. It does not test whether stations tend to drop to a fresh low on a particular weekday. If your version of the folklore is really “discounts reset on Tuesdays,” that’s a different question about timing the bottom, and it’s the one we’ll take apart next. And this is petrol — ULP and E10. Diesel runs its own cycle, so if you’re filling a diesel, Tom’s onto that one separately.