Scott Piechocinski roamed the rows of a CarMax dealership in Charlotte, N.C., on a recent afternoon, searching for something small to replace his son’s 2001 Nissan Pathfinder sport utility vehicle.

He’s not alone: As gas prices marched higher and now top $3.50 per gallon across the nation, car buyers across the country increasingly are abandoning SUVs and pickups in favor of smaller crossovers and cars.