When Should You Fill Your Tank? Uncovering the Best Time to Buy Gas and Save Big

Summer is coming, and so are higher gas prices. If you want to figure out the best time to buy gas without burning through your wallet, timing really does matter—more than you might think.

Temperature Is Your Secret Weapon

Here’s something most drivers don’t realize: the temperature of the day directly impacts how much fuel you actually get for your money. When you fill up during the hot afternoon hours, gasoline expands due to the heat. This means the same amount of money buys you less fuel than it would on a cooler day.

The physics is simple—warm gas takes up more space, so you’re paying the same price for fewer gallons. Conversely, filling up early in the morning or late at night when temperatures drop allows the gasoline to contract slightly, giving you more fuel for your dollar. While the pump stores fuel underground where temperature fluctuations are minimal, the pump handle itself can get hot in the sun, still affecting the liquid volume. So if you’re serious about the best time to buy gas, aim for those cooler hours.

Monday Is Your Best Bet; Thursday Is Your Worst

According to GasBuddy, one of the leading fuel-tracking apps with years of price data, gas prices fluctuate significantly throughout the week. Their analysis shows that Monday offers the cheapest gas prices, making it the ideal day to fill your tank if you’re watching your budget.

On the flip side, Thursday is historically the most expensive day at the pump. Planning your fill-up around this weekly cycle could add up to meaningful savings over time, especially if you adjust your driving schedule slightly to accommodate Monday visits to the gas station.

Geographic Location Makes a Massive Difference

Where you live dramatically affects what you pay per gallon. GasBuddy’s research reveals stark differences: some states enjoy prices under $3.25 per gallon, while others pay over $4.50.

The most affordable states include Mississippi, Arkansas, Louisiana, Oklahoma, and Alabama—each offering significantly lower prices than expensive regions. Within these states, specific metro areas stand out even more. Jonesboro (Arkansas), Tyler (Texas), and Gulfport-Biloxi (Mississippi) are among the cheapest markets, with prices hovering around $3 per gallon. Compare that to California’s most expensive metros—San Rafael, Santa Rosa, and Napa—where prices exceed $5 per gallon in many cases.

If you’re relocating or planning a road trip, choosing your route through these cheaper regions can result in substantial fuel savings.

Summer Brings Double Trouble

Summer-grade gasoline blends cost more to produce and distribute, adding up to $0.15 extra per gallon. But that’s just part of the story. Summer also triggers peak driving season—school breaks, vacations, road trips—which drives up demand and consequently prices.

Combine this seasonal surge with the temperature effect mentioned earlier, and summer afternoons become the most expensive time to fill up. You’re paying premium prices and getting less fuel in return.

The Practical Bottom Line

Finding the best time to buy gas involves multiple strategies working together. Yes, filling up at dawn or midnight helps—but the savings are incremental, not dramatic. You’ll see better returns by downloading a fuel-tracking app like GasBuddy to monitor local price trends, adjusting your fill-ups to Mondays, avoiding Thursdays, and reducing unnecessary driving.

Location matters too. If you have flexibility in where you live or travel, choosing a region with cheaper fuel infrastructure saves far more than timing alone. The real win comes from combining these tactics: use an app to track prices, fill up on Mondays in cooler hours, and avoid premium summer-time fill-ups whenever possible.