TL;DR: Brisbane ULP sits at 173.9 c/L today (19 Jul) across 440 metro stations — the top of its last 30 days and 20 days past the 151.9 trough. The average lap runs about 37 days: up sharp in about 7, down slow over about 30. The cheap window has closed. But this rise is running slower than usual, so calling an imminent peak is a lower-confidence read than the pattern implies.
The question drivers actually ask isn’t “how does the cycle work” in the abstract. It’s the one a bloke on r/brisbane put plainly: it’s an up/down cycle that “can mean the difference between spending $1.90/L and $2.30/L.” So the only thing worth knowing on any given day is where we are in that swing.
The claim
Everyone who’s watched the bowser for a year feels the shape of it. The felt injustice is always the same, and Vinnie on Whirlpool put it better than any chart:
“when the price is going down it takes a week to ten days to come down by 20-30 cents, but when it goes up its just matter of hours to go up by 30 cents” — ‘Vinnie’, Whirlpool
Up fast, down slow, every lap. That’s the claim. Here’s whether the numbers hold it.
What we checked
Every price in this post is the Queensland Government price feed — the actual price each station reported charging, not a driver’s guess at the bowser.
We took every ULP (regular 91) report from the Brisbane-metro stations inside 30 km of the CBD, carried each station’s last known price forward day by day, and took the median across the panel for every day from July 2025 to now. On a typical day about 440 of the 473 in-range stations report — the panel averages 434 a day and never drops below 431 outside the ramp-in — so that daily median is a solid read on the market level. Then a change-detection pass walked the peaks and troughs, and we measured the swings between them.
One note up front, because it matters. There’s a known data gap from early March to late April this year where reports went quiet, so the carry-forward invents a fake ramp to 259.9 c/L through March. That’s an artefact, not a real price event. Every cycle figure below excludes that stretch entirely, and no measured swing crosses it, so what survives is five complete, clean trough-to-peak-to-trough cycles.
What the feed shows
The lap length. Across those five clean cycles, a full lap runs about 37 days peak to peak, tight in a 35-to-41 range.
The shape. The rise, trough to peak, takes about 7 days (median 6). The fall, peak back to trough, takes about 30. Add them and you get the lap back: 6.8 up plus 30.4 down is 37.2 — the cycle length, to the day. The fall is more than four times slower than the rise. Vinnie was right. Prices rocket up in a week and then grind down for a month, every lap.
The size. The trough-to-peak swing on this window runs about 45 c/L — 46 on this particular stretch, which is the same number our own myth-bust post measured over a longer window. The small difference is the window, not a disagreement: that post started in January 2025 and caught some flatter early-2025 months, while this one leans on the bigger spring-and-summer swings. Round either way and it’s about half a dollar a litre between the bottom and the top of a lap.
Here’s the shape, drawn to scale: the sharp up-leg, the long grind down.
Where we are now
The last trough was 29 June at 151.9 c/L. Since then the median has climbed +22.0 c/L to 173.9 today, day 20 of this cycle, across 440 metro stations. Against its own last 30 days, that 173.9 is at the very top — the 30-day high. On a within-cycle read, this is a local high and a poor day to fill.
Two things keep that honest.
First, this cycle is behaving oddly. The pattern says the rise is a sharp seven-day, roughly 46 c/L spike. Twenty days in, this one has only managed +22 c/L — about half a full up-leg, spread over nearly three times the usual rise window. It’s still climbing, up about 4 c/L in the last three days and printing fresh 30-day highs, so the direction isn’t in doubt. But this is a slow grind up, not the usual rocket, which means calling an imminent peak here is lower-confidence than the historical cadence would suggest. If the market has more room to run off that 151.9 trough, waiting today doesn’t mean waiting for much cheaper tomorrow.
Second, “top of the last 30 days” is a local read, not a verdict on the year. This is high for this lap. Whether it’s dear against the whole 12 months depends on where the next peak lands, which this slow climb hasn’t settled yet.
The verdict
The claim holds. Up fast, down slow is exactly what 37-day laps do: about 7 days up, about 30 days down, a swing of about 45 c/L each lap. And today sits near the top of the current lap — 173.9 c/L, the 30-day high, 20 days off the bottom. The one caveat on the verdict is that this up-leg has been slower than the pattern, so “near the top” is a confident read but “at the peak” is not yet.
So what
If you’re a commuter and your tank can wait, this isn’t your week. You’re on the up-leg, past the 29 June bottom, and the cheap days have been and gone. The next honest fill window is the glide-down after this peak turns, and on the average lap that’s still a couple of weeks out.
If you’re near empty and can’t wait, that’s fine. A fill is a fill, and the cycle doesn’t care about your schedule. You can watch the metro median and your own regular servos on the map at fill.pinly.com.au and decide from the number, not the folklore.
The honest limit
This is a median across about 440 stations — a market level, not a promise about any one servo. Individual stations lead and lag by days, and one Brisbane driver has clocked where it starts:
“You can always (at least for 12 months now) spot the new cycle starting first around North Lakes.” — ‘harleyb170’, Brisbane, Whirlpool
So the cycle tells you the weather, not what your corner charges this afternoon. Check the map for that. And a straight number caveat: this rests on five clean cycles once the March–April data gap is excluded. They’re tight, but a wider clean run would firm them up. This is ULP/91, Brisbane metro only. Diesel runs a different, flatter cycle, and none of these numbers carry to it.