Americans are driving more miles than they have in years, but that doesn't mean they are using more gasoline.

Data collected by the U.S. Federal Highway Administration (FHWA) shows that vehicle-miles traveled (VMT) has increased consistently over the past 18 months.

In August--the most recent month with available data--277.3 billion miles were driven. That's the most in August of any year of VMT monitoring by the agency.

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Overall driving mileage increased from 2.9 to 3.1trillion since April 2014, and surpassed the pre-recession high last December, reports CNN.

Analysts also calculate "seasonally-adjusted" data intended to account for seasonal variations in travel, and allow comparisons any months of a given year.

The seasonally-adjusted VMT for August 2015 was 263.3 billion miles--a 3.6-percent increase over August 2014.

Traffic at the I-10 & I-405 interchange in Los Angeles, California (by Mario Roberto Duran Ortiz)

Traffic at the I-10 & I-405 interchange in Los Angeles, California (by Mario Roberto Duran Ortiz)

That's the largest single-month percentage gain recorded since 2002, the FHWA says.

However, it's only a 0.4 percent increase over the July figure, indicating that the August figure is part of a long-term trend.

But while VMT is increasing significant, the amount of gasoline consumed is holding relatively steady.

ALSO SEE: Miles Driven Are Rising, But Gas Consumption Continues To Fall

U.S. drivers consumed 136.7 billion gallons of gasoline in 2014 (2015 data isn't available yet) according to the Energy Information Administration.

That's about a 1.7-percent increase over the amount consumed in 2013.

This is because while Americans are driving more, the cars they are driving are also getting more efficient.

Gas pump

Gas pump

The sales-weighted average fuel economy for new cas was 25.3 miles per gallon for the first nine months of 2015, according to data from the University of Michigan Transportation Research Institute.

That means it's currently matching the average for calendar-year 2014, which in turn was an increase over 2013's 24.7 mpg, and 2012's 23.8 mpg.

As carmakers shake off the last vestiges of the recession and car sales climb, they devoutly hope that those improvements continue.

In today's climate of cheap U.S. gasoline, however, the steadily growing proportion of SUVs and crossover utility vehicles in total sales hampers that goal.

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Still, continually-rising Corporate Average Fuel Economy rules mean that every new version of a given model is at least somewhat more efficient than the version it replaces.

Still, U.S. consumers will have to actually trade in their older cars for the benefits to be fully realized.

A survey published earlier this year found that the average age of a car on U.S. roads is a record-high 11.5 years.

If miles driven stays steady, as it did for several years, less gasoline is burned. When miles grow, as they did this year, we still burn less gas than we otherwise would have.

In other words, once more: The fuel-efficiency standards enacted for model years 2012 through 2025 are doing just what they were intended to do.


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