With temperatures in some parts of the Bay Area this week reaching triple digits, the problem is worse than usual. But some consumer advocates suspect you're being shortchanged on gas year-round.
As temperatures go up, so does the price of gas. Gas always gets more expensive in the summer when we drive more for vacations, but included in the price of gas is a hidden cost.
"It comes to an average in California year round about four cents a gallon of loss," says Judy Dugan with Consumer Watchdog.
That's because gas expands and contracts with the temperature.
"Any liquid when it gets hot gets bigger, it expands. When it gets cooler, it contracts," says Jim Sweeney, the director of the Precourt Institute for Energy Efficiency at Stanford University.
The federal standard for the temperature of gas is 60 degrees. At 60 degrees, when you pay for a gallon of gas, you get a gallon of gas, but when gas is 72 degrees, you're getting about one percent less gas than you're paying for. Seventy-two degrees just happens to be what the California Energy Commission says is the average temperature of gas in this state. It's known as hot fuel. A trade group for independent gas stations says it's no big deal.
"From our point of view, it is not a significant variation. To the best of our understanding, there is a plus or minus five-degree error margin used by the Division of Measurement Standards in their accuracy testing," says Jay McKeenan, VP of the CA Independent Oil Marketers Association.
But motorists already paying $1.43 a gallon more than a year ago weren't too happy to hear about it.
"It makes me sad. Everybody's sad... getting less than they should get," says Brian Royball of Oakland.
One possible solution is to put automatic temperature compensation equipment on fuel pumps. The pumps would then dispense greater volumes of gas when temperatures rise above 60 degrees and less gas when temperatures drop below 60 degrees.
"Our feeling right now is that whatever comes up is going to be way more expensive to the consumer than any proposed solution on the table right now," says McKeenan.
Adding the equipment would cost about $2,000 to $3,000 a pump, a move that Consumer Watchdog in Los Angeles supports.
"If you amortize that over eight years or 10 years or the life of the pump, it's a pretty small cost," says Dugan.
In Canada, gas stations voluntarily add the temperature compensation equipment to their pumps.
"They did it voluntarily because it benefited them. In Canada, gasoline is on average colder than 60 degrees," says Dugan.
The Energy Commission is studying whether the idea makes economic sense for both retailers and consumers in the U.S.
"I think it's politically viable to mandate the adjustment. I don't know whether it will be ultimately in the interest of the customer or harmful for the customer to do so," says Sweeney.
The Energy Commission is expected to release its study in September.
See below for the breakdown of the temperature of gasoline measured county by county.