The Environmental Protection Agency recently issued new testing procedures that will cause fuel economy estimates on the stickers of new vehicles to drop an average of 12 percent for city driving on most 2008 model year vehicles, and 8 percent for highway driving, according to The Associated Press. Highly fuel-efficient vehicles are expected to see the largest decrease, with ratings for city driving dropping by as much as 30 percent and highway estimates falling 25 percent from current levels. Mileage estimates for gas-electric hybrids probably will be 20 to 30 percent lower for city driving and 10 to 20 percent lower on the highway, the agency said. The changes respond to consumer complaints that fuel economy estimates are frequently less than advertised. EPA's new system will take into account data from vehicle tests designed to more accurately assess high-speed driving, rapid acceleration, the use of air conditioning and driving in cold temperatures. The agency said the test methods will help bring the estimates on the window stickers closer to the miles per gallon that drivers achieve on the road. Test results will not be used to determine whether automakers comply with laws requiring the U.S. fleet to have an average fuel economy of 27.5 miles per gallon for cars and 21 mpg for sport utility vehicles, pickup trucks and vans. Those requirements are found in the Corporate Average Fuel Economy program, which is run by the Transportation Department and has separate regulations to determine fuel economy, The Associated Press reports. For the first time, the agency will require fuel economy labeling of medium-duty vehicles, which weigh between 8,500 and 10,000 pounds, including SUVs and vans. Automakers will be required to post the labels on the vehicles beginning with the 2011 model year. Auto industry officials noted that mileage estimates differ based on vehicle speeds, quick stops and starts, routine maintenance and whether the vehicle is hauling cargo in the trunk. "Even with the new labels, mileage will vary," said Charles Territo, a spokesman for the Alliance of Automobile Manufacturers. The trade group released a new Web site detailing the changes: http://www.mileagewillvary.com.