Petrol and diesel prices at Asda Swindon Haydon Supercentre

Asda Swindon Haydon Supercentre, SN25 4BG.

What it is charging

Unleaded: 169.7p a litre, 2.0p under the national average, filed Tuesday 27 October
Diesel: 197.7p a litre, 1.0p under the national average, filed Tuesday 27 October

Mfg Fleming Way: 167.9p a litre, 3.0 miles away. 1.8p a litre cheaper: saves 99p a tank, and costs about £1.14 of fuel to get there and back. Not worth the trip.
Mfg Marlborough Road: 167.9p a litre, 4.5 miles away. 1.8p a litre cheaper: saves 99p a tank, and costs about £1.71 of fuel to get there and back. Not worth the trip.
Ascona Coped Hall Service Station: 168.9p a litre, 4.9 miles away. 0.8p a litre cheaper: saves 44p a tank, and costs about £1.88 of fuel to get there and back. Not worth the trip.
Mfg Penhill: 169.9p a litre, 1.5 miles away
EG Swindon Pfs: 169.9p a litre, 2.4 miles away
Bridge End Service Station: 169.9p a litre, 2.7 miles away

On a 55-litre tank at 40mpg. The distance is straight-line rather than by road, so a real trip is longer than the one costed here.