The Snowdonia 360 is a signed touring loop of around 360 miles that circles Eryri and takes in Anglesey, the Llŷn Peninsula and the North Wales coast. It's designed to be driven over several days, with plenty of stops. Fuel use varies a lot along the way, because the route swings between flat coast roads and some of the steepest mountain passes in Wales.
Mountains and coast in one loop
On the coastal sections, including much of Anglesey and the Llŷn, a car settles into steady, economical driving. In the mountains it's different. The A4086 through the Llanberis Pass climbs to Pen-y-Pass, at around 359 metres, with a long gradient and narrow sections where traffic bunches behind slower vehicles. Expect to lose 15 to 20% of your normal economy on these passes, and more in a heavily loaded car.
Welsh speed limits
Since September 2023, the default speed limit on most restricted roads in Wales, typically in towns and villages, has been 20 mph. The loop passes through many small towns, so journey times are longer than the mileage suggests. Driving steadily at 20 mph uses little fuel, but repeated slowing and speeding up between villages does add some. Plan days around time rather than distance.
A worked cost
For the full loop in a car averaging 40 mpg, at an illustrative 140p a litre, fuel comes to about £57. If you only have a day, the shorter internal mountain loop of around 80 miles costs about £13 at the same economy, or around £15.50 allowing for an 18% penalty on the passes.
Parking matters more than fuel
At popular trailheads such as Pen-y-Pass, parking is limited and in busy periods often needs to be booked in advance, while the Sherpa'r Wyddfa bus links the main villages and car parks around Yr Wyddfa. Leaving the car at a valley base and using the bus for a mountain day saves fuel and the frustration of circling full car parks.
Refuelling and charging
Forecourts are plentiful around Bangor, Caernarfon and Porthmadog, and you'll find fuel in Betws-y-Coed and Dolgellau, but some upland stretches have none. Electric car drivers will find chargers in the larger towns; check availability before heading into the mountains.
Islands, peninsulas and ferries
Two of the loop's highlights sit at its edges. Anglesey is reached by one of two bridges across the Menai Strait, both free, and its coast road is gentle and economical. The Llŷn Peninsula is quieter, with narrow lanes leading to small beaches and harbours. Neither requires the steep climbs of the mountains, so they're good places to spend days when you want easier driving.
Weather in the mountains
Eryri is one of the wettest parts of Britain, and conditions in the passes can change quickly. Mountain weather forecasts are more useful than general ones for planning a day in the hills. In winter, the higher passes can be icy even when the coast is mild, and the mountain roads may close in snow.
Taking time
At 360 miles, the full loop is best spread over at least four or five days. Rushing it means long days at the wheel and little time for walking or exploring. Choosing a couple of bases, one on the coast and one in the mountains, cuts the amount of driving each day.
A second example: a mountain day
A day based in Betws-y-Coed, crossing the Llanberis Pass to Caernarfon and returning via Beddgelert, covers about 60 miles. At 40 mpg with an 18% penalty on the passes, at an illustrative 140p a litre, that's about £11.60 of fuel.