Want to save money at the pump? Fill up on Monday morning on your way to work.
That's the advice of GasBuddy, the fuel-savings app that tracks real-time data from more than 150,000 gas stations throughout the country.
In a study provided exclusively to USA TODAY, GasBuddy assessed the best day to fill up and the worst day to fill up nationwide and in each state.
While Monday is the best day on average nationwide to fill up, Friday is the worst day. (Scroll down to see state-by-state details on the best and worst time to get fuel.)
"Very early in the week, when gas stations are generally a little bit quieter traffic-wise, is a great time to fill up," said Patrick DeHaan, head of petroleum analysis for GasBuddy. "We generally see more volatility and higher prices later in the week."
On Mondays, some prices tick upward in the afternoon, so it's often a good idea to fill up in the morning. On Fridays, prices often spike in part because some stations are seeking to make more money ahead of weekend trips.
Stations are busiest on Friday afternoons around 5 p.m., according to GasBuddy.
Drivers who fill up exclusively on Friday could save $20 to $30 more year by switching to Monday, according to GasBuddy.
There are exceptions. For example, Tuesday is the best day to fill up in 19 states.
Living in Utah? The best day is Sunday. Hawaii? Try Wednesday.
While the national average price of gas peaks on Fridays, Saturday is the worst day to fill up in 16 states, while Sunday is the worst day in 12.
The best day to buy gas, by state:
Monday: Alaska, Arizona, California, Colorado, Connecticut, District of Columbia, Florida, Idaho, Illinois, Indiana, Kentucky, Maine, Massachusetts, Michigan, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Oregon, Rhode Island, South Carolina, South Dakota, Vermont, Virginia, Washington, West Virginia, Wyoming
Tuesday: Alabama, Arkansas, Delaware, Georgia, Iowa, Kansas, Louisiana, Maryland, Minnesota, Mississippi, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, Wisconsin
The worst day to buy gas, by state
Saturday: Alabama, Connecticut, Hawaii, Kansas, Maine, Maryland, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, Oregon, South Carolina, South Dakota
Sunday: Arkansas, California, Colorado, Delaware, Georgia, Iowa, Oklahoma, Rhode Island, Tennessee, Texas, Virginia, Wisconsin
Friday: District of Columbia, Kentucky, Louisiana, Massachusetts, Minnesota, North Carolina, North Dakota, Pennsylvania, Vermont, Washington
Thursday: Arizona, Florida, Idaho, Illinois, Indiana, Michigan, Ohio, West Virginia
Wednesday: Alaska, Nevada, New York, Wyoming