Many Mobil and Exxon stations in California have begun posting small signs on each pump, calling it a “Motor Fuel Measurement Notice.” The Foundation for Taxpayer and Consumer Rights (FTCR), however, feels that the stickers–warning that the energy content of a gallon of fuel varies with its temperature–acknowledge that consumers have been ripped off.

The FTCR have released a statement claiming that the stickers are a strategy to fend off “hot fuel” lawsuits and allow the rip off to continue. The foundation noted that either a current class action lawsuit or federal legislation to require temperature compensation of retail fuel may force oil refiners to fix the problem.

“ExxonMobil, America’s most profitable corporation, owes drivers more than a cheap sticker in tiny print,” said Judy Dugan, research director of FTCR and its OilWatchdog.org project. “The company has funds that it uses to help dealers with infrastructure, and which could be used to buy nozzles that adjust fuel volume for higher temperatures.”

Newly introduced legislation in the Senate, by Sen. Claire McCaskill of Missouri, would require gasoline and diesel to be sold adjusted for temperature, giving motorists a fair gallon’s worth of energy for their money.

“Consumers and lawmakers are increasingly aware that there is a thumb on the scale when they buy gasoline, even though they have no fairer alternative for purchasing it,” said Dugan. “The Senate’s hot fuel bill is a warning to oil companies, refiners and distributors of gasoline that they can either make gasoline sales honest themselves or be forced by the courts or government to do it.”

Exxon said that it would put stickers on its pumps at stations in California and Arizona. A FTCR-conducted survey of six stations in Los Angeles and Santa Monica, however, found the stickers only at Exxon-owned and franchised stations, not at independently owned but branded Exxon and Mobil stations.