Methodology

To find the least fuel-efficient cars for 2023, 24/7 Wall St. reviewed greenercars.org ratings of 2023 model year cars based on the report GreenerCars 2023: Efficiency and Weight — Not Just Electric vs. Gas — Shape Environmental Impact. Greenercars.org is part of the nonprofit research organization American Council for an Energy-Efficient Economy (ACEEE). To avoid repetition, only the lowest scored model for each car is included. Also, because the Chevrolet Silverado and GMC Sierra are identical, GreenerCars also included the Silverado.

The organization determines its ratings based on fuel economy and emissions results from different sources as well as estimated pollution from vehicle manufacturing, from the production and distribution of fuel and from vehicle tailpipes. The combined emissions estimate factors into a Green Score that runs on a scale from 0 to 100, with 100 being least polluting and 0 most polluting. The environmental damage index reflects the cost to human health from all emissions in cents per mile.

Most data is from the report, except for five-year extra spending in fuel costs for each vehicle compared to an average vehicle, which came from the Environmental Protection Agency’s fueleconomy.gov site. The manufacturer suggested retail price came either from the EPA site or from Car and Driver.