Ask MRN: Is Monday the cheapest day of the week to buy gas?

Dear MRN,

I recently read a story online that claimed the cheapest day of the week to buy gas is Monday. Is that true?

GasBuddy released a study in February 2022 that determined Monday offered the lowest average gas prices in 2021 in most of the United States, including Illinois, Michigan and Virginia. Monday also was the best day to buy gas when GasBuddy did similar studies in 2017, 2018 and 2019. Thursday topped the list as the most expensive day of the week in the 2022 study.

Patrick DeHaan has analyzed and tracked oil markets and fuel prices for nearly two decades. He started with GasBuddy in 2009. He says work is incomplete for a 2023 study on the best day to buy gas.

“Here’s the thing about any kind of study like that,” he said. “It’s meant to be somewhat of a guidance, but it’s always circumstantial. It’s like, when’s the best time to buy a house? There are days of the week that may be better or worse, but there’s no definitive rule. There are different ways to look at it. 

“I wouldn’t change what we said a year ago, because it was applicable, and the data was true at the time. However, certainly the situation from a year ago is much different, and we haven’t done a study for this year.”

GasBuddy, a travel and navigation app, is used by more North American drivers to save money on gas than any other app. GasBuddy covers more than 150,000 gas stations in North America, giving drivers 27 ways to save on fuel. 

DeHaan said GasBuddy looked at average gas prices and every state average for the 2022 study.

“We did it by state, because it can vary, but we did a lot of comparisons and looked at the direction and movement of prices,” he said. 

The numbers compiled in the study showed which days were best for gas purchases. However, how much money one can realistically save on gas by filling up on one day depends on several factors — what kind of vehicle someone drives (and its gas mileage), as well as how much someone drives over the course of a typical month or year.

DeHaan also said the numbers couldn’t tell why certain days were better.

“I don’t think there’s a great answer,” he said. “We can only look at the data that we have at the time. It’s tough to have hypotheticals here in front of me to say if someone filled up on 50 Mondays that they would be $15 ahead. It’s very difficult to put an exact science to it because of the wide variety of human behaviors, and it’s quite circumstantial. If the market moved in a certain way, was it enhanced by the stock market? I don’t know that I can come to a perfect conclusion.

“The only Golden Rule when it comes to filling your tank is to check prices around you. We can still try to come up with some conclusions that help people have better odds. If you were to always stick with Monday, for example, we find that overall, you will probably come out a winner. That’s what we’re essentially aiming for. It’s not always surefire, but the odds are that you’ll do better.”