Petrol and diesel prices around Wales

Welsh fuel prices are best understood by looking at the geography. The population sits mostly along two coastal strips, the M4 corridor in the south and the A55 in the north, with a large and thinly populated middle. Those two corridors carry nearly all the competitive pricing in the country; the middle carries very little of it.

Along the M4 between Newport, Cardiff, Bridgend and Swansea you get the full range of supermarket forecourts trading against each other, and prices there track the English average closely. Barry, Cwmbran and Pontypridd in particular tend to sit at the sharp end of the Welsh tables because several operators are packed into a small radius.

The A55 does the same job across the north, feeding Wrexham, Colwyn Bay, Bangor and the traffic heading for Holyhead and the Irish ferries. Ferry timetables give that route a steady rhythm of vehicles that need fuel at predictable hours, which keeps the stations near the terminal busy and reasonably keen on price.

Mid Wales is the part that catches people out. Between Machynlleth, Builth Wells and Llandovery the stations are sparse and the roads are slow, so a detour to find a cheaper pump often costs more in time and fuel than it saves. Aberystwyth, Carmarthen, Newtown and Welshpool are the practical places to fill before heading into Snowdonia or the Brecon Beacons.