Dave5

For MY2022, the EPA says that the average real-world CO₂ emissions for all new vehicles fell by 10 g/mile to 337 g/mile, the lowest average it has ever measured. Similarly, real-world fuel economy increased by 0.6 mpg for MY2022, to 26 mpg—this, too, is a record high and the single-largest year-on-year improvement for both CO₂ and mpg for nine years.

And it’s not a one-off. Despite the occasional off year, the EPA’s data shows that since 2004, US passenger fleet emissions have decreased by 27 percent, or 123 g/mile. And over the same time, average fuel economy has increased by 35 percent, or 6.7 mpg. Even better, the EPA says its preliminary data shows even greater declines in carbon emissions and greater increases in fuel efficiency for MY2023.

https://arstechnica.com/cars/2023/12/2023-had-the-best-improvement-in-fuel-efficiency-in-9-years-says-epa/