DETROIT – There are miles and then there are “Seth miles.”

Both measure 5,280 feet, but a “Seth mile” is different. More extreme. More grueling. More punishing. All that rigor is part of the durability story of the 2012 Chevrolet Sonic.

“Seth miles” are named for Chevrolet Sonic Quality Manager Seth Valentine. Each mile Valentine puts on a test vehicle is called a “Seth mile” by Sonic engineers because of his reputation for extreme testing on long road trips.

Valentine’s duty: Make the Sonic the most reliable and durable small car in North America.

The efforts are paying off as Sonic more than doubled the sales of its predecessor, the Aveo, in January. Sonic is the only subcompact built in the United States.

Over one six-week period, Valentine drove more than 14,000 miles in the first Sonic to leave the General Motors Orion (Mich.) Assembly Plant.

Valentine drove Sonic Vehicle Identification No. 1 from north to south and east to west, across subtropical Florida, the arid deserts of Arizona, the mountains of Colorado, and the South Carolina low country.

In addition to amassing miles with other Sonic team members, Valentine would play typical consumer and pack the Sonic to the hilt for a family vacation.

Valentine’s attention to technical detail makes him a road warrior with a cause.