But now a new report questioning that shortage has Sen. Maria Cantwell pushing the Department of Justice to get involved.
"I want the Department of Justice and the Federal Trade Commission to investigate refinery by refinery whether these reports are true or not," Cantwell said.
In their report, Oregon-based McCullough Research claims in May and October, several refineries said they had to shut down gasoline production because of fire, like the one at Cherry Point in Anacortes, or for maintenance reasons when actually those refineries weren't shut down at all.
And citing thousands of environmental documents, McCullough accuses those same refineries of creating an imaginary shortage and driving up prices by 50-cents a gallon.
If the report is true, it meant drivers on the West Coast were paying more for a gallon of gas than anywhere else in the country and more than we should have been -- and the oil companies pocketed the profits.
Tupper Hull with the Western States Petroleum Association -- a spokesperson for all west coast refineries -- says some refineries did shut down, but still produced emissions levels that may have looked like they were up and running.
He blames the spike in gas prices on real supply and demand.
"There was no subterfuge or misconduct on the part of the refineries," Hull said.
But Cantwell countered it wasn't just supply and demand.
"Supply is up, prices are up - what's going on?" she wondered.
Cantwell says any refinery found guilty of manipulating gas prices could be fined $1 million for every day they spiked. But, she first has to convince federal agents to investigate.
She says fellow senators from Oregon and California are also putting the pressure on.
A 50-cent spike in prices would have mean on average, drivers would have paid an extra $20 a month.