With regard to reducing fuel consumption and CO2 emissions of road transport consumers' adoption of fuel-efficient vehicles is crucial. However, facing the ongoing trend of increasing car size and power, fuel consumption is apparently of lesser importance to most buyers. For the design of effective measures to change behavior and promote fuel-efficient cars, psychological factors should be considered. Drawing from psychological research on environmental behavior, we propose a model which integrates psychological variables to explain the purchase of fuel-efficient vehicles by private consumers. This model is tested with survey data from 302 Swiss respondents whose households have bought a new car since 2002. SEM analyses confirm valence of less power and smaller size, and perceived behavioral control as direct predictors of the purchase of a fuel-efficient vehicle. Problem awareness, symbolic motives, and response efficacy influence the respective behavior indirectly via affecting the direct predictors. The design, implementation and evaluation of measures aimed at changing car choice behavior with respect to fuel consumption should account for these factors.