Hummer dealers try to boost fuel economy with unauthorized mods

Some Hummer dealers are so desperate to boost the fuel economy ratings of their vehicles that they're willing to void warranties -- and possibly even break the law. According to a report in today's Wall Street Jorunal, Detroit Hummer and Hummer of Novi are installing a device called the "Mileage Maximizer" that they claim will give the H2 and H3 over 25 miles per gallon in highway driving. The so-called "Vortex Valve" is said to boost fuel economy by 30%, according to the manufacturer. GM says installing any such device will void the warranty of its vehicles. Meanwhile, a spokesman for the U.S. Environmental Protection Agency said such modifications sometimes boost emissions along with milage. "It's safe to say, in general, that in any situation, tampering with the emissions controls devices on any vehicle certified by the EPA is against the law," he said. [See full WSJ report - registration required.]