Mazda has been dethroned.
Being the most efficient automaker in the United States doesn't come with any special prizes but it is still a coveted title amongst automakers who lord the statistic over competitors. For the past several years, Mazda has held the title of the most efficient automaker, since the company doesn't sell any pickup trucks or a single engine with more than four cylinders. But as of the 2018 model year (the latest year in which full data is available from the Environmental Protection Agency), Mazda has been dethroned.
The 2019 EPA Automotive Trends Report ranked Honda first in fuel economy among full-line automakers. Honda only ranked second overall because Tesla doesn't build a single car with an internal combustion engine. With a fleet average "real world" fuel economy of 30.0 miles per gallon (mpg), Honda is now the most fuel-efficient automaker in the US.
Honda's fleet average of 30 mpg marks a five-year improvement of 2.8 mpg, sitting 4.9 mpg above the industry average. The company's emissions were similarly impressive at 296 grams of CO2 per mile, an improvement of 31 grams/mile from 2013 and 57 grams/mile better than the industry average. Honda has improved its fuel economy rankings with the introduction of several hybrid, plug-in hybrid, and electric models,
The Honda Insight is the company's most fuel-efficient vehicle with up to 55 mpg (not counting the all-electric Clarity) while the upcoming CR-V Hybrid should heavily improve the company's hybrid sales numbers. Honda says two-thirds of its automobile sales will be electrified by 2030, with many being built in America including the Insight, Accord Hybrid, CR-V Hybrid, Acura MDX Hybrid, and NSX.
Honda does have a few larger and less efficient models like the Civic Type R, Passport, Pilot, and Ridgeline but those haven't done enough to offset the fuel sippers mentioned above. Toyota may offer a broader range of hybrid vehicles at the moment, but it also sells lots of gas-guzzling pickup trucks. At least for now, Honda can celebrate its status as the most efficient automaker in the US.