Forrestfield Diesel Holds at 200 Cents While Perth's Eastern Suburbs Defy a Rising Western Australia

The biggest price movement in the country this week did not happen in a capital city. Up on the Dampier Peninsula, well north of Broome, unleaded petrol fell 40.9 cents to 279.1 cents per litre. That is the kind of swing remote communities rarely see, and it tells you something about how volatile fuel pricing becomes once you leave the metro grid.

Closer to home the picture is steadier, but still worth a look. Across Western Australia, the average diesel price edged up just 1.0 cent to 236.9 cents per litre on 18th May 2026. A modest move on its own. What the data shows underneath that average, though, is a genuine split between Perth's eastern and southern suburbs and the rest of the state.

Forrestfield leads the cheap diesel cluster

Forrestfield is sitting at the bottom of the table. Its five diesel sites average 203.7 cents, with the cheapest pump reading 199.9. That is more than 33 cents below the state average, and the spread between Forrestfield's dearest and cheapest servo is only 10 cents, which suggests genuine competition rather than one outlier dragging the number down.

It is not alone. The numbers tell an interesting story across Perth's industrial belt:

A closer analysis reveals these are not coastal or tourist suburbs. They are working areas with freight depots, trade businesses and high diesel turnover, and that volume tends to keep prices honest.

The Bassendean outlier

Bassendean deserves its own mention. Its cheapest diesel sits at 197.3 cents, the lowest single price in the metro data, yet its dearest site charges 227.9. That is a 30.6 cent spread inside one suburb. Statistically speaking, a motorist filling an 80 litre ute in Bassendean could pay roughly 24 dollars more or less depending purely on which servo they pull into. It is a useful reminder that the suburb average is only half the picture.

Where Western Australia sits nationally

This represents a notable contrast with the eastern states. NSW diesel averages 236.5 cents, South Australia 236.6, Queensland 237.3 and Victoria 238.2. Western Australia, at 236.9, is squarely mid pack. The difference is that WA carries the widest range of any mainland state, with a gap of 206.7 cents between its cheapest and dearest diesel. That range is what makes checking price trends before you fill genuinely worthwhile here.

WA's price cycle also works differently to the eastern capitals. Perth runs a clear weekly rhythm, and knowing which day sits at the bottom can save more than chasing a single cheap suburb. The best time to fill up guide breaks down how that cycle behaves.

Diesel and the freight question

Diesel matters here beyond the family car. WA's mining and agricultural freight runs on it, and a one cent move at the state level multiplies quickly across a fleet. For now, the gentle 1.0 cent rise is encouraging compared with the heavier increases seen elsewhere, where NSW diesel climbed 11.8 cents and South Australia added 10.0 cents in a single day. Anyone tracking diesel prices week to week will notice WA has been the calmest mainland market this round.

The takeaway

The data indicates geography matters a great deal in WA right now. Drivers in Perth's eastern and southern industrial suburbs are filling up around 30 cents cheaper than the state average, while remote pumps swing 40 cents in a week. If you are anywhere near Forrestfield, Kwinana Beach or Welshpool, the cheap diesel is on your doorstep right now. If you are not, the 30 cent suburb to suburb gap means a short detour can still pay for itself.

The numbers are clear: in Western Australia this week, where you fill up is worth more than when.