ALLEN COUNTY, Ind. (WOWO): What is the best day of the week to fill up your gas tank? It may be on Mondays, according to GasBuddy.com.

Gasoline prices are currently the most expensive they’ve been in more than 19 months and will continue to increase with the summer driving season approaching. Therefore, GasBuddy, conducted a study that found the best and worst days of the week to buy gas when it comes to optimal savings.

GasBuddy analyzed fuel price data over a three year time period and found that Monday offers the lowest average, making it the best day to fill the tank. Turns out the price at the pump is typically cheaper in 23 states on Mondays.

Thursday is the worst day to buy gas, having the most expensive average.