TL;DR: Three weeks ago I told you Brisbane diesel had stopped climbing, flat at 254.9 c/L for a week — a pause, I said, because wholesale had paused, not a peak you could time. The plateau broke. The metro diesel median is now 289.9 c/L in today’s live pull — up 35 cents since that 254.9 flat, and it’s climbed almost every day: 273.9 on 16 Sep, 285.5 by 18 Sep, up to 289.5 by 23 Sep. The dearest metro servo is 298.9 — a hair under $3.00 a litre. Why it broke: the plateau meant wholesale had paused, and it didn’t stay paused. The crude-and-dollar surge I wrote up on 16 Sep — Brent near US$109, up ~20% in a month, a weaker Aussie dollar — turned the wholesale line back up, hard. Diesel tracks wholesale on a two-week lag with no discount cycle to cushion it, so it took the full force. The gap to petrol is now about 50 cents (diesel 289.9 vs petrol 239.7), the widest in our window, and diesel is 25c over even premium 98. No cheap week is coming — it never does for diesel. The only lever is which servo: cheapest diesel today is 269.5, about 20c under the median, roughly $16 on an 80-litre fill.
I drive a diesel ute, so I’ll own this one plainly: three weeks ago I called the flat. Diesel had stopped dead at 254.9, seven days running, and I told you not to read it as a peak — it was a pause, because wholesale had paused, and it’d sit there until wholesale turned. That was the honest read of the data in front of me. Then wholesale turned, and the plateau didn’t just end — it broke and went vertical. This is the sequel, and it’s the ugly one.
The plateau broke
Here’s the number that matters. On 30 August the metro diesel median was 254.9 c/L, flat as a table. Today it’s 289.9 in the live pull — up 35 cents in three weeks, and it didn’t drift there. The daily median climbed almost every single day: 260.9 on 10 Sep, 265.9 by the 14th, then 273.9 (16 Sep), 279.5, 285.5 (18 Sep), 286.9, and 289.5 by 23 September. The dearest metro servo is now 298.9 — one cent under three dollars a litre. That’s not a wobble off a plateau. That’s the flat breaking and the line standing straight up.
Why it broke — the plateau was never a peak
I said this in the plateau post, and it’s the whole reason this happened, so I’ll say it again short: a flat diesel pump doesn’t mean diesel has topped out. It means wholesale stopped rising about a fortnight ago. Diesel tracks the wholesale Terminal Gate Price on roughly a two-week lag, and it doesn’t run the petrol discount cycle — so it sits at whatever wholesale says and moves when wholesale moves. The plateau was wholesale catching its breath. It didn’t stay caught.
What restarted it is the thing I wrote up a week ago. On 16 September every Brisbane grade lurched up 16 to 21 cents together — 91, 95, 98 and diesel in lockstep, which is the signature of a wholesale move, not the cycle. The cause was upstream of every servo: Brent crude around US$109 a barrel, up about 20% in a month, on top of a weaker Aussie dollar. A dearer barrel bought in US dollars, paid for with a softer Aussie — those two forces compound, and they turned the wholesale line back up, hard.
Diesel took the full force of it. That’s the part worth sitting with. Petrol at least has a cycle — the majors hoist it to a peak, then drift it back down, so a petrol driver gets the occasional cheap week even in a dear month. Diesel has no such cushion. There’s no sawtooth to ride down. It just eats the wholesale move, cent for cent, on the lag. So when the barrel surged, diesel is the grade that took it cleanest and hardest — which is exactly why the plateau I described three weeks ago broke into the steepest climb we’ve charted.
A premium-98-plus-25c world
Here’s where diesel now sits against everything else on the forecourt. The gap to petrol is about 50 cents — diesel 289.9 versus a petrol median of 239.7 — the widest in our window. And diesel is now 25 cents over even premium 98 (264.9). Read that again: a diesel driver is paying a premium-98-plus-25c world. The fuel that used to run about 10 cents over regular petrol is now clear of the dearest bowser fuel most servos sell.
None of that is diesel “going crazy” against the others — it’s diesel doing exactly what a wholesale-tracking fuel does when wholesale surges and there’s no cycle to blunt it. The petrol grades will get their discount weeks back as the cycle rolls. Diesel won’t. It stays pinned to wholesale until wholesale eases.
What it means for your fill
- The tradie maths is brutal, and it’s not you doing anything differently. On an 80-litre ute fill, 35 cents a litre since the plateau is about $28 more per fill than three weeks ago — same ute, same tank, same drive. That’s the surge, landed, before you’ve changed a single habit.
- This is a wholesale leg, not a cycle peak — don’t wait it out. A plateau breaking upward is wholesale turning up, and it holds until crude eases or the dollar recovers. I can’t date either. Waiting for diesel to “come back down off the top” the way petrol does is the petrol reflex, and it doesn’t map onto a diesel tank. No cheap week is coming. It never does for diesel.
- Your only lever is which servo — and it’s the one thing you control. The cheapest diesel in the metro today is 269.5 c/L, about 20 cents under the 289.9 median, with the dearest up at 298.9. On an 80-litre fill that spread is roughly $16, today, no waiting. In a dear week, the map is the discount.
- Shop the map, not the calendar. Pick diesel on fill.pinly.com.au, see the spread across the metro, and drive to the cheap end. Every price there is the one that station reported to the Queensland Government feed — not a stranger’s guess at the bowser.
The short version: three weeks ago diesel was flat at 254.9 and I told you it was a pause, not a peak. The pause ended, wholesale turned up on the crude-and-dollar surge, and diesel — with no cycle to cushion it — took the full 35-cent hit to 289.9, a hair under three dollars at the dearest servo. There’s no cheap week coming for a diesel tank. The only $16 on the table is the one between the cheapest servo and the median, and that one’s yours to take today.
How we measure: Brisbane-metro stations within a box around the CBD, QLD Government price feed, last-known price carried forward to a daily median. Diesel is the “All Diesel” family — the cheapest diesel-family price per station, standard or premium, because many metro sites file diesel only under the premium code; it’s what a diesel driver actually pays. Petrol is regular unleaded (ULP/91), premium is 98, and the gaps are median-to-median. Today’s live figures — median 289.9, cheapest 269.5, dearest 298.9 — are from the latest price each station reported to the feed; obvious data errors are excluded. The daily climb (273.9 on 16 Sep through 289.5 on 23 Sep) is the daily-median tail. The crude (~US$109, +~20% month) and Aussie-dollar figures are external market data reported by others — the barrel’s direction, not something measured against our feed. This is a read of where diesel sits today, not a forecast: a wholesale leg holds until wholesale turns, and I can’t tell you the day.
— Tom