The source said since the "Wonderland" singer was ticketed by the California State Patrol June 3 for a missing license plate on his own vehicle, he has been using the former "Friends" star's multiple cars to travel around the city, E! Online reports.
"Obviously, she trusts him," the anonymous source said. "She lets him drive her car even though his car is parked at her house."
An unidentified source also said that while the celebrity couple has not been dating long, Mayer appears to have convinced the actress to be open about their romantic life.
"Before, she was kind of a ghost, but now she is out a lot more," the source told E! Online. "With her other relationships she has been a little more secretive, but this one she is not hiding."