Australia Petrol & Diesel — 2026 Two-Scenario Forecast

Reading the chart. The solid blue line is observed Australian retail petrol price for the five largest cities, from the pre-conflict baseline (week ending February 20) through Jun 23. The shape tells the story of the year so far: a sharp run-up from 177 to 263 cents per litre between Feb 28 (Hormuz closure) and end-March (compounded by the April 15 Geelong refinery fire mid-cycle), followed by a steady recovery — now at ~172 c/L, below the pre-conflict baseline — on the federal government's 32 c/L excise cut (April 1), easing international refined benchmarks (Brent $78.2, war premium nearly fully unwound), and the Geelong RCCU restart (Jun 23). The two pivot events that drove the old forecast uncertainty are NOW RESOLVED. Both scenarios now show a partial ~16 c/L cliff on Jul 1 (the excise drops from 32 c/L to 16 c/L at Jun 30); they diverge on Aug 2: Scenario 1 (green) extends the remaining 16 c/L; Scenario 2 (red) lets the full 16 c/L expire, adding another +16 c/L jump on Aug 2.

Scenario 1Partial cliff Jul 1 (16 c/L), then remaining 16 c/L extended beyond Aug 2. The 32 c/L excise drops to 16 c/L on Jul 1 — a mechanical +16 c/L jump to ~188 c/L (already confirmed; this is NOT in question). The remaining 16 c/L is then extended again on Aug 2 on cost-of-living grounds. Geelong RCCU restarted Jun 23 at >90% capacity, adding domestic refining volume. International benchmarks stay soft (Brent $78.2, war premium nearly fully unwound). MSO petrol stocks at the highest level since the MSO began. Retail petrol holds in a 183–188 c/L band after the Jul 1 step-up, ending December at approximately 180 c/L; diesel ~213 c/L.

Scenario 2Partial cliff Jul 1 (16 c/L) + full expiry Aug 2 (another +16 c/L). The 32 c/L excise drops to 16 c/L on Jul 1 — identical to Scenario 1, a mechanical +16 c/L jump to ~188 c/L. On Aug 2, the remaining 16 c/L expires unrenewed (another +16 c/L mechanical jump to ~204 c/L), regardless of crude direction. This is the live policy risk for Aug 2 — the government extended only to Aug 2, and signals may harden toward expiry. After the Aug 2 step-up, retail eases gently as soft benchmarks feed through (Brent $78, Geelong restarted), ending December near 196 c/L rather than the old ~250 c/L the pre-deal model carried; diesel near 226 c/L. The pain is two small policy cliffs rather than one large one — softer than the old feared scenario, but still a real real-world impact.

The excise decision (RESOLVED for Jun 30, PENDING for Aug 2)Jun 30 settled: partial extension at 16 c/L to Aug 2. Aug 2 is the new decision date. The Australian fuel excise was halved from 52.6 to 26.3 cents per litre on April 1, 2026, with states and territories agreeing to forgo GST revenue on fuel (~5.7 c/L) — a combined consumer-facing reduction of about 32 c/L. Rather than allowing the full 32 c/L to expire unrenewed on Jun 30 (feared outcome) or extending the full relief (hoped outcome), the government confirmed Jun 23 that a 16 c/L discount will remain in force until August 2. This means: on Jul 1 there IS a ~16 c/L step-up (from full excise cut to half excise cut) — real but half the feared impact. After Aug 2, the cabinet must decide again: extend the remaining 16 c/L (Scenario 1) or let it expire in full (+16 c/L mechanical jump on Aug 2, Scenario 2). The two scenarios on this page now bracket the Aug 2 decision, both showing the Jul 1 partial cliff as given. GEF will update this page after each official ACCC print (Fridays, Australia time) and immediately upon any Aug 2 decision or further cabinet announcement.

Geelong & the MSOAustralia's import-dependence story, and the buffers that exist against it. Australia imports approximately 90% of its refined liquid fuels (petrol, diesel, jet) as a structural feature of its energy market — only Geelong (Viva Energy, Victoria) and Lytton (Ampol, Queensland) remain operating, and together they cover under 20% of national demand. Most refined product arrives from Singapore, South Korea and Japan, whose refineries are themselves significantly supplied by Middle Eastern crude — so the Strait of Hormuz reaches Australia by one-step indirection. Geelong RCCU RESTARTED Jun 23: Viva Energy confirmed the Residue Catalytic Cracking Unit is back online at >90% of normal capacity. The Alkylation unit remains offline and "repair or replacement options are being assessed" — Geelong expected to operate at slightly reduced capacity into 2027. The Minimum Stockholding Obligation (in force since 2022) requires industry to hold roughly 21 days of forward consumption cover. As of the latest PM&C taskforce update (mid-June), stocks of diesel and petrol are above average — with petrol stocks at the highest level since the MSO began. None of this prevents a price increase from the Jul 1 partial cliff — buffers protect against physical shortages, not tax changes — but they do explain why the GEF Australia pin remains on watch rather than escalating to confirmed shortage.

MethodThis is a scenario forecast, not a prediction. The observed Feb-Jun line is built from ACCC Weekly Fuel Price Monitoring reports plus the PM&C Fuel Supply Taskforce page (multiple consecutive improving official prints through the ACCC June 12 reading, the latest plotted point). The Jun-Dec branches are illustrative model paths, not guarantees; the real outcome will depend on the federal cabinet's June decision on the excise cut, the actual restart date and ramp-up rate of the Geelong RCCU, the pace of any US-Iran diplomatic settlement, whether Iran follows through on its Bab el-Mandeb extension threat, international refined-product benchmark movements through summer (which is winter in Australia), and weather-driven demand. The model is anchored on the ACCC June 12 reading and the May 4 Viva Energy guidance, and is refreshed after each official print (ACCC publishes Fridays, Australia time) — and immediately upon any cabinet excise decision or confirmed Geelong restart. Re-weighted June 16 after the US-Iran interim deal unwound the Hormuz crude premium. Sources: ACCC Weekly Fuel Price Monitoring Reports (March 27 to May 29, 2026); PM&C Fuel Supply Taskforce public-information page; Viva Energy May 4 ASX disclosure on Geelong RCCU restart; Australian Taxation Office April 2026 excise duty rates; DCCEEW MSO weekly reporting; Australian Institute of Petroleum public statements; IEA Oil Market Report May 2026. Per-disruption detail and the live AU shortage map at global-energy-flow.com/shortages/australia/.