The cheapest day to fill four utes? For diesel, there isn't one

In 2026 there is no reliable cheapest weekday for most fleets. Diesel never follows price cycles, and the ACCC says petrol cycles have mostly not occurred in Sydney, Melbourne, Brisbane and Adelaide since late February 2026. Perth still has a weekly petrol cycle, and WA and Victoria publish tomorrow's prices the afternoon before.

Why doesn’t the “fill up on Tuesday” rule work for a work fleet?

Because it was only ever about petrol, and only in five cities. The ACCC tracks price cycles in Sydney, Melbourne, Brisbane, Adelaide and Perth for regular unleaded. It says plainly that retail diesel and LPG prices do not move in price cycles, and that cycles do not occur in Canberra, Hobart, Darwin or most regional locations.

That matters if your utes run on diesel. A diesel fleet gains nothing from waiting for a cycle low. What saves money is the gap between two servos on the same day.

The second problem is that the cycle has largely gone quiet. The ACCC notes that since the Middle East conflict began in late February 2026, petrol price cycles have mostly not occurred in Sydney, Melbourne, Brisbane and Adelaide. Advice written before then about which weekday to buy is describing a pattern that has, for now, mostly stopped.

How long were the petrol cycles, when they were running?

For the petrol vehicles in your fleet, it still helps to know the rhythm in case it comes back. The ACCC’s averages for 2025:

Cycles of five or six weeks are hard to plan a fleet around. Most of the time the price is either climbing or sitting high. A driver who fills whenever the tank is low will pay mid-cycle prices most of the time, and asking four drivers to time it isn’t realistic.

The ACCC publishes a buying tip for each of the five cities on weekdays (at least Monday, Wednesday and Friday) around midday. It is free and worth a glance before a big fill. It is also, by the ACCC’s own description, a guide only.

Is Perth different?

Yes, in two ways, and both help you.

First, Perth and Mandurah still run a short, predictable petrol cycle. WA’s Consumer Protection says the cycle currently starts with a sharp rise every Wednesday, then prices fall over the next six days, so the last day of the cycle is the cheapest. The ACCC’s own table for May and June 2026 shows the same pattern: lows on Tuesdays, peaks on Wednesdays. Regional WA prices are generally more stable and do not cycle, and neither diesel nor LPG does.

Second, WA tells you tomorrow’s price today. Every fuel retailer in the state must notify FuelWatch of the next day’s prices by 2pm. Those prices are locked in for 24 hours from 6am the following day, and FuelWatch publishes them by 2:30pm.

In WA, you can see at 3pm what every servo will charge tomorrow, and the price can’t change on you overnight.

For a WA fleet, that makes it a fair afternoon job to check tomorrow’s prices along the routes your vans will run, and tell drivers where to fill.

What changed in Victoria this year?

Some fuel-saving guides still say Victoria has no official fuel-price scheme. That is out of date. Victoria now has a daily price cap, and it publishes tomorrow’s prices the afternoon before.

From 10 March 2026, under Victoria’s Fair Fuel Plan, every retailer must set and report a maximum price — a cap — for each fuel type for the next day. During the day prices can only go down from that cap, not up. Retailers must also report any price change within 30 minutes. The prices feed into Servo Saver in the Service Victoria app.

According to Service Victoria, caps reset at 6am and last 24 hours. Each retailer’s cap for tomorrow is published on Servo Saver by 4pm the day before. Between 4pm and 6am the app shows both the current price and tomorrow’s cap, so you can decide whether to fill tonight or wait.

One caveat from Service Victoria: there is no ceiling on what a station can set as its cap. The cap stops a price jumping during the day. It does not make fuel cheap.

What do NSW, Queensland and South Australia require?

These three states run real-time reporting rather than a next-day price. The price you see is the price now, reported shortly after it changes at the bowser.

Two details are worth knowing before a driver argues with a console operator:

• Discounts are not included. NSW defines the FuelCheck price as the standard price without discounts or shopper dockets. WA’s FuelWatch shows standard cash prices, excluding discounts and card fees.
• There can be a lag. Queensland, South Australia and Victoria allow 30 minutes to report a change. Service Victoria warns that if the pump disagrees with the app, the station may still be inside that window.

How do you actually find the cheapest fuel across four vehicles?

The manual way works. It is just five different apps, and it relies on each driver remembering to check. For an owner-operator, a workable routine looks like this:

1. 1Know which vehicles cycle. Petrol vehicles in Perth can be timed to the weekly low. Diesel vehicles everywhere cannot, so for them it is purely about which station.
2. 2Check the official source for your state. FuelCheck in NSW, Servo Saver in Victoria, FuelWatch in WA. In Queensland and SA, prices from the official scheme are published through third-party apps.
3. 3In WA and Victoria, use the afternoon preview. Both states publish tomorrow’s prices the afternoon before.
4. 4Avoid brimming the tank at the top of a cycle. The NRMA’s advice, reported by the ABC, is to top up with smaller amounts when prices are high.
5. 5Record what you actually paid. Litres, price and odometer, per vehicle. Without that, you have no way of knowing whether any of this is working.

The last step is the one most fleets skip. It is also the only one that tells you which van costs the most to run. Our guides on petrol versus diesel running costs and what the excise change costs four utes both start from those per-vehicle records.

When is a spreadsheet and the state app enough?

If all your vehicles are in one state, run on the same fuel and refuel near the depot, the official app plus a fuel column in your spreadsheet is fine. You do not need software for that.

It starts to break when drivers fill wherever the job takes them, when you run petrol and diesel side by side, or when receipts sit in glove boxes until the end of the quarter. Then the problem isn’t finding fuel. It’s that nobody has a per-vehicle number.

Where does Axlerun fit?

The Axlerun fuel locator draws on the live government fuel-price feeds in NSW, Queensland, South Australia, Victoria and Western Australia. It shows the cheapest nearby fuel, and nearby EV chargers, inside the same app drivers already use for the logbook. It is free on every plan, including Drive, which is free for your first three vehicles.

Each fill-up can be logged against the vehicle with litres, price and odometer, alongside servicing, tolls and fines. On Cruise, the locator also runs on CarPlay and Android Auto, so a driver can check prices on the dashboard rather than on a phone.

It does not change what the ACCC or state schemes say. Diesel still won’t cycle, and Victoria’s caps still reset at 6am. What it changes is that drivers check the price before filling, not after, and you end the month with a fuel cost for each vehicle rather than one total on the card statement.