The pain at the gas pump is palpable. Making it worse: Consumer groups say a summertime gas station secret cheats drivers out of billions of dollars. And chains are fighting against changing the rules. TODAY National Investigative Correspondent Jeff Rossen reports.
More from TODAY.com
Hillary Clinton: Granddaughter led me 'to speed up' political plans
Clinton said she is inspired to keep working to ensure that Charlotte and her generation are provided equal opportunities ...
- Lauren Hill, inspirational college basketball player, dies
- Marathon dad's victories help raise money for son with spina bifida
- Will it work on Vale? Savannah tries tissue sleeping trick at home
- Listen to the chilling 911 call Sandra Bullock made during break-in
- Hillary Clinton: Granddaughter led me 'to speed up' political plans
We're all feeling the squeeze from gas prices. But consumer watchdogs like Judy Dugan say many drivers don't even know the half of it.
When it's hot outside and the gasoline is warm, she says consumers aren't getting what they're paying for.
"Every time you stick that nozzle in your tank on a hot day you're being cheated," Dugan told TODAY. "It's a huge rip-off of American drivers."
When gas gets hot, it loses energy. That means your car gets fewer miles per gallon. Fill it up at 60 degrees and the typical car can go 500 miles. But fill it up when it's 90 degrees and you get 10 miles less out of that same tank.
But you're still paying the same amount at the pump.
"There's no way that we can tell what kind of value you're getting when we pull into the gas station," Dugan said.
According to a 2007 Congressional report, Americans paid an estimated $1.5 billion extra for gas that summer. And gas prices have skyrocketed since.Video: Are you being overcharged at the gas pump? (on this page)
A solution exists: Gas pumps with special meters would give you the right amount of gas for your money based on the heat. But stations are fighting against implementing it.
"We simply don't agree that the juice is worth the squeeze," said Dan Gilligan, an official from the Petroleum Marketers Association of America. Gilligan said gas stations are already giving consumers the best deal they can, and drivers benefit in cold weather. Installing the new pumps would be too expensive, he said, and we'll wind up paying more anyway.
"Putting a $2.4 billion cost on gas station owners would only transfer $2.4 billion to the consumer," Gilligan said.
In Canada, they've been implementing the technology for nearly two decades. Ninety percent of gas stations use pumps that measure and adjust for temperature. When it's hot, they'll give you more gas for your dollar. Consumer advocates say you get what you pay for there, no matter the weather.
More Rossen Reports
American drivers have filed class-action lawsuits against gas station chains in 21 states, calling the practice fraud and hoping to force gas stations to install the high-tech pumps.
As part of a legal settlement, Costco agreed to install the new pumps at its gas stations in warm weather states, pending court approval. And now, three of the big oil companies — BP, Shell and ConocoPhillips — are settling too, though the details of the deal are still unclear.
Other gas station chains continue to fight the lawsuits and will be in court next month.
Have an idea for a future edition of Rossen Reports? We want to hear from you! To send us your ideas, click here.
© 2013 MSNBC Interactive. Reprints