DETROIT — Fiat has added 5 percent to its majority ownership of Chrysler.

The Italian automaker got the added stake by making a car in the U.S. that gets 40 miles per gallon of gas. With the added shares, Fiat owns 58.5 percent of Chrysler.

The U.S. government, which bailed out Chrysler and funded its 2009 restructuring under bankruptcy protection, gave Fiat a 20 percent stake in Chrysler in July of 2009 in exchange for Fiat’s management expertise and use of its technology. Fiat gradually raised its ownership by meeting performance goals and buying the government’s stake in Chrysler.

Chrysler said early Thursday that a pre-production version of the new Dodge Dart compact got 40 mpg in testing by the Environmental Protection Agency in late December.