The Energy Information Administration, the analytical arm of the department, said gasoline consumption for the first half of 2013 was 0.6 percent, or about 50,000 barrels per day, lower than the same period last year.
"So far in 2013, year-over-year economic growth and slightly lower retail gasoline prices, a combination that would generally lead to increased gasoline consumption, have been more than offset by the increased fuel efficiency of the light-duty vehicle fleet," it said Thursday.
The EIA said the consumption trend is a continuation of observations made during 2012, when gasoline consumption also declined by 50,000 barrels per day year-on-year.
The motor group AAA posted an average retail price for a gallon of regular unleaded gasoline at $3.54 Friday, 24 cents lower than the same time last year.
The EIA said retail gasoline prices for the week increased modestly for all regions of the country, notably in the Midwest.