May U.S. auto sales beat expectations by achieving an 8 percent gain over a year ago, industry consultant Autodata Corp said on Monday.

Total sales on a seasonally adjusted annualized rate were 15.3 million vehicles, Autodata said.

Analysts polled by Thomson Reuters had expected a gain of 6 percent to 15.1 million vehicles on an annualized basis.

(Reporting by Bernie Woodall; Editing by Richard Chang)