Volkswagen of America

John and Helen Taylor, the Australian hypermilers who made news in the United States in 2009 by averaging 67.9 miles per gallon in a tour of the 48 contiguous states, recently added another record to their considerable tally. The couple drove 1,626.1 miles in a 2012 Volkswagen Passat TDI SE from Houston to Sterling, Va., breaking the Guinness record for the longest drive in a passenger car on a single tank of diesel fuel.

They departed May 3 and passed through nine states, averaging 84.1 miles per gallon during the excursion, and finished on May 5. By Wednesday the Taylors were on a plane, en route to their home in Australia.

“We drove the Passat only two days prior to the record drive, and test results showed figures of 93, so we were very encouraged,” Mr. Taylor wrote in an e-mail, referencing the miles per gallon he and his wife observed in pre-drive testing. “We believed we could reach Sterling Shell Station, Va., which we managed to achieve without running out of diesel.”

Their record more than doubled the 795-mile highway range estimated for the Passat TDI by Volkswagen, based on a highway fuel-economy rating of 43 m.p.g. Volkswagen provided a showroom-stock Passat for the Taylors’ record attempt.

The couple improved on the previous record, 1,526.6 miles, set in a 2010 Passat 1.6 BlueMotion diesel in Europe by Gavin Conway, a writer for The Sunday Times. Both cars had fuel capacity of 18.5 gallons and had 6-speed manual transmissions. The Taylors typically share driving duties, but on this trip Mr. Taylor drove slightly more, he said, while his wife monitored social media from the front passenger seat.

To simulate real-world driving conditions, the Taylors brought along 120 pounds of luggage and limited their driving to daylight hours. “We wanted the drive to be realistic, hence daylight driving and carrying holiday luggage, inspiring Americans to save on their upcoming summer driving holidays,” Mr. Taylor said. Based on current diesel prices, the Taylors calculated their per-mile fuel cost at 4.65 cents.

“The hardest part of the drive was getting stuck in several long traffic jams, but we remained calm and worked through it,” Mr. Taylor added. The couple shared some tricks for eking out gaudy fuel-economy numbers with The Times in 2009, after completing the 48-state tour in the Jetta TDI. Further tips can be found at the couple’s Web site, FuelAcademy.com.

The Taylors have been setting fuel-economy records since 1982, having set or broken well over 40. Such dedication has earned them the unofficial title of the world’s most fuel-efficient couple.

“We work always as a team to achieve not only driving goals but in our marriage,” Mr. Taylor said. He views the road trips as an opportunity for cultural enrichment and marriage maintenance. On the road, he and his wife talk “about how we brought up the kids, how we can educate the world about efficiency, listening to music, learning German, telling my wife how much I love sharing these dream drives with her.”

Their next record attempt is scheduled for September — a drive around Australia.