Car dealer group Sonic Automotive has posted a 39% rise in quarterly earnings, boosted by cost improvements and growth in all its business units.

According to Reuters, the Charlotte, North Carolina-based company said profit rose to $US26.8 million, or 61 cents a share, from $19.3 million, or 45 cents a share, a year ago.

The company said it earned 65 cents a share from continuing operations, higher than Wall Street expectations of 61 cents.