Blairgowrie Filling Station: 167.9p a litre, 4.2 miles away. 1.0p a litre cheaper: saves 55p a tank, and costs about £1.60 of fuel to get there and back. Not worth the trip.
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.