According to the fuel-savings app GasBuddy, Monday is the best day to save money on gas, while Friday is the worst day to fill up
Those who normally fill up on Fridays can save between 20 and 30 bucks a year by switching to Mondays
The best and worst days can depend on where you live though, with Saturday being the worst day in 16 states, and Sunday being the worst in 12
Source:USA Today