2017 Toyota Prius Prime, Dallas, TexasEnlarge Photo
Rating cars isn't just about acceleration times—or at least it shouldn't be.
Unlike other car rating organizations, the Automotive Science Group rates cars according to their life-cycle CO2 emissions, based on a combination of their fuel economy and weight, as a proxy for the materials consumed in their production, as well as social and economic factors in their production.
This year, the Toyota Prius Prime earned the group's Best All-Around Performance title for its 133-MPGe EPA rating, its 25-mile electric range, low manufacturing footprint, and end-of-life recyclability.
The awards are intended to guide new-car buyers, and thus focus on the first 6.5 years and 100,000 miles of a car's life—the average first-ownership cycle for a new car.
ASG notes the Prius's rapid improvement in social and environmental factors since its introduction 18 years ago. For example, every new Toyota Prius uses biodegradable upholstery and dashboard materials. ASG expects the Prius Prime to emit 181 grams of CO2 per mile, counting its manufacturing. and disposal.
Although the Pius Prime proved the greenest car for new-car buyers who want to minimize their social and carbon impact, several all-electric cars proved even greener than the Prius Prime over their full life cycles, including the Tesla Model 3, the Chevy Bolt EV, Nissan Leaf, and Ford Focus Electric.
2018 Tesla Model 3Enlarge Photo
Over its predicted lifetime, the Tesla Model 3 is expected to emit 161 grams of CO2 per mile. The Chevy Bolt EV is expected to emit 164 grams per mile, and the 2017 Nissan Leaf, 167 grams.
Since most new-car buyers don't hold onto their cars for their full life cycle, ASG rates new cars based on a normal ownership cycle of 6.5 years.
The carbon footprint of producing lithium-ion batteries is front-loaded into the sales of new cars, and offset gradually over time by lower energy consumption in the ASG study.
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Electric cars, especially those with big batteries, take longer to make up for the production of their batteries.
The rating include vehicles' performance against social standards set by the United Nations, including social performance, including respect for human rights, labor practices, environmental responsibility in manufacturing. Counting those factors alone, small, inexpensive cars scored big: the Mitsubishi Mirage (and Mirage G4), Nissan Versa, and Chevrolet Spark. These economic factors also weigh more heavily early in a car's life,
The top-scoring non-plug-in hybrid was the Toyota Prius C, at number 17, followed by the Hyundai Ioniq Blue hatchback.
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