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The 2011 Kia Optima Hybrid is estimated to get a solid 40 mpg on the highway. But a team of “hypermiling” specialists—who utilize special driving techniques to boost a vehicle’s fuel economy—just finished a trip through every Lower 48 state while averaging 64.55 miles per gallon. They broke a Guinness World Record in the process.

Wayne Gerdes, of Illinois, and New York’s Chris Bernius teamed up to complete a 14-day, 7,899-mile drive that touched each of the contiguous 48 states—and that, most impressively, required just 5.5 fill-ups at the pump. Throughout their journey, in a standard-issue 2011 Kia Optima Hybrid, the drivers averaged 64.55 mpg, and 1,418 miles on the road before having to refill the tank.

How did they do it?

Driving a vehicle with decent fuel-efficiency helps. But the way you drive your car can also have a huge impact on how many miles to the gallon it gets.

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Gerdes and Bernius are hypermilers—experts who pride themselves on getting the absolute highest mpg possible. A few years ago, Mother Jones published a feature about Gerdes, in which he competed for the title of Most Fuel-Efficient Driver in the World and managed to get 59 mpg in a regular old Honda Accord.

Among the techniques used by hypermilers are: emptying the vehicle of all but the essentials to cut weight; drafting behind 18-wheelers; accelerating and turning extremely slowly; and using the brakes only when absolutely necessary. Gerdes and others can sometimes pull a vehicle to a full stop without stepping on the brakes.

The general idea here is that drivers will save more on gas by losing less behind the wheel. In addition to taking proactive steps like properly inflating tires and removing excess weight from the trunk, a laid-back approach to driving—laying off the brakes, gently pressing the gas pedal rather than being a leadfoot—have a big impact on improving fuel economy.

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Two new studies—from the University of Michigan (courtesy of USA Today) and UC-Riverside (reported on by Wired) back up the idea that how one drives, and how a vehicle is maintained, greatly affect how much the driver will wind up paying over time for gas.

Taking the recommended approach can net the driver a 45% savings in gas over the course of a year, no matter what vehicle we’re talking about. On the other hand, that means that if you’re accustomed to flooring it and disregarding the Check Engine light, you’re wasting a ton of money on gas.

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Brad Tuttle is a reporter at TIME. Find him on Twitter at @bradrtuttle. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.