DETROIT — The 2017 GMC Acadia sport utility vehicle that is just starting to arrive in dealerships around the country is 700 pounds lighter than the version it replaces, and can go 23 miles on a gallon of gasoline, up from 18 m.p.g., a 28 percent improvement.

One of the secrets to the big weight loss? Glue.

Many of the steel parts of the Acadia’s underbody are held together not by rivets or welds but by advanced adhesives similar to those used in modern airplanes like the Boeing Dreamliner. Since this ultra-superglue bonds parts together all along the seam where they connect, not just in certain spots, the parts become stiffer. Because of the stiffness, General Motors is able in many cases to switch to thinner steel, helping the new Acadia shed pounds.

The grades of steel are thinner by only about the width of a human hair, but “it’s all the little things that add up to the big number,” said Charlie Klein, executive director of G.M.’s global carbon-emissions reduction strategy.

Automakers are racing to improve fuel efficiency to meet the increasing mileage standards that environmental regulators have set for the next nine years. Space-age adhesives are being used more widely, just one of the many leaps manufacturers are taking to reduce weight and save fuel.