gasoline engines, as the carmakers downsized these vehicles’ engines from six to four cylinders to maximize fuel economy. The evaluation found that the MKZ Hybrid reduces greenhouse emissions by 46.2% as compared to its sibling gasoline-only MKZ, and the Lexus CT200h a 42.9% reduction. Besides the Prius, the 2011 evaluation found that more automakers are using hybrid technology to increase fuel efficiency and decrease tailpipe emissions without imposing significant price premiums for those benefits, and other hybrids scoring high on environmental improvement include the Ford Fusion Hybrid, Honda Civic Hybrid, and Toyota Highlander Hybrid. In the non-luxury category, the worst offender is the Volkswagen Touareg Hybrid, which reduces less than a 10% of greenhouse emissions, an all-time low on the scorecard. According to the UCS, the "Touareg was singled out as an example of a "muscle" hybrid that emphasized power over fuel efficiency." The UCS also singled out among the worst-rated hybrids for environmental improvement the new Porsche Cayenne S Hybrid, the BMW Active Hybrid 750i, and the ActiveHybrid X6. The UCS explained that the Chevrolet Volt plug-in hybrid (PHEV) was not included in the evaluation even though the Volt could have been compared with the Chevrolet Cruze as the conventional similar. The reason for the exclusion is that PHEVs are affected by a variety of factors that affect their environmental performance, such as the type of fuel used (coal, wind, solar, etc.) for generating electricity to charge the vehicle, and also by the driving habits, including how often the vehicle is plugged in and the number of miles driven on electricity-only mode. See also Government incentives for fuel efficient vehicles in the United States Green vehicle Hybrid electric vehicle Hybrid electric vehicles in the United States List of hybrid vehicles References External links Fueleconomy.gov: EPA's fuel economy ratings Hybrid Analysis - Total Cost of Ownership for 2013 model year hybrids, Vincentric, October 2013. UCS Hybrid Scorcard webpage Hybrid electric vehicles Green vehicles Environmental indices