> fuel tank capacity 12 gallons > let's say it's $3.5/gal here and $3.67/gal down there > fuel efficiency 10l/100km = 2.64gal/62.13mi > drive takes 20 min, let's say say it's just 20 km = 12.4 mi (probably more though) > you spend 0.528 gallons to get there and 0.528 gallons to get back > that's $3.7 > you save 12 x $0.17 > that's $2
Switzerland