Mileage estimates likely to decline under EPA’s proposed new system

The U.S. EPA has proposed new standards for calculating auto fuel-economy ratings, expected to reduce by 5 to 30 percent the mileage estimates in window stickers on new cars and trucks. Ouch. It’s the first ratings overhaul since 1985, intended to reflect changes in driving conditions (e.g., more stop-and-go traffic) and technology (e.g., more fuel-eating air-conditioners). The city-driving mileage estimates for hybrids — including Toyota’s hot-selling Prius, which gets a 60-mile-per-gallon estimate under the current system — are likely to shrink an especially dramatic 20 to 30 percent. Environmental groups are voicing support for the proposal, but are disappointed that the new estimates won’t be used when determining manufacturers’ compliance with Corporate Average Fuel Economy standards — and thus won’t lead to real fuel efficiency gains. The proposed standards are open for 60 days of public comment and expected to take effect with 2008 model-year vehicles.