Time to rethink 'miles per gallon'

摘要

Recent experiences with high-profile battery-electric, plug-in hybrid, and extended-range electric vehicles have inspired industry-wide head-scratching about the best way to measure cars'energy use. The confusion only gets worse as gasoline and fossil-fuel diesel are joined by greater amounts of compressed natural gas, biodiesel (algae being a promising source), cellulosic ethanol, electrical energy (from various sources), perhaps widespread hydrogen (I'm not counting on it)-and who knows what else you chem majors are stewing up in your garages. If you've followed the government's efforts to produce more instructive Environmental Protection Agency mileage stickers-spotlighted by the Nissan Leaf's and Chevrolet Volt's-you've noted the subject's vocabulary is necessarily, and rapidly, expanding well beyond "mpg."