The average gas mileage of cars varies depending on weight class and vehicle type, but the average 2014 and 2015 miles per gallon among passenger cars driven in the United States is just over 25 mpg, according to the University of Michigan. Each year in the United States, the Environmental Protection Agency compiles a list of vehicles falling into the categories of light duty or commercial vehicles. This data set accounts for cars with the lowest fuel economies, which have combined fuel economies less than 20 mpg, as well as those with the highest, which exceed 100 mpg.
In the EPA's 2015 fuel economy summary, data focuses on statistics from vehicles with different types of fuel sources, including those using standard gasoline and electric-gasoline hybrids. The data also evaluates cars based on their combined gas mileage of standard performance in city versus highway driving.
Cars included in the EPA's statistics come from many different manufacturers, and officials compile data regardless of vehicle sales numbers, price and make. Among the least fuel-efficient cars are midsize and sports cars, which average around 10 mpg, while combined fuel-electric cars can average over 100 mpg.
The EPA has recorded fuel data from cars in America since 2007. At that time, the average fuel economy of cars in the United States reached just over 20 mpg. The EPA updates its data monthly and includes statistics from outlying makes and models.