A spike in oil prices over recent days amid a resumption of fighting, however, threatens to push gas prices higher, erasing some of the relief delivered last month.
Oil prices on Monday fell to their lowest level since March after U.S. officials announced an agreement between the United States and Iran.
Hundreds flocked to a Belmont Gardens neighborhood Shell Station for gas at $1.99 a gallon.
The IRGC said U.S. forces attacked Sirik island.
In its 50-year history, Costco has never seen such demand for gas.
Illinois' gas tax is set to automatically increase by about a cent this July 1.