The benefit-cost analysis of standards to reduce vehicle greenhouse gas emissions and improve fuel economy by the U.S. Environmental Protection Agency (EPA) and the Department of Transportation (DOT) displays large net benefits from fuel savings for new vehicle buyers. This finding points to an energy efficiency gap: the energy-saving technology provided in private markets appears not to include all the technologies that produce net private benefits. The gap exists if the costs of energy-saving technologies are lower than the present value of fuel reductions, and "hidden costs"- undesirable aspects of the new technologies - do not exceed the net financial benefits. This study examines the existence of hidden costs in energy-saving technologies through a content analysis of auto reviews of model-year 2014 vehicles. Results suggest that it is possible to use fuel-saving technologies on vehicles without imposing hidden costs. For each technology examined, reviews with positive evaluations outnumbered those with negative evaluations. Evidence is scant of a robust relationship between vehicles' use of energy-saving technologies and negatively rated operational characteristics, such as handling or acceleration. Results do not provide evidence for hidden costs as the explanation of the efficiency gap for vehicle fuel-saving technologies. Published by Elsevier Ltd.