I, too, have spent many an hour searching for the name behind the lovely voice on the Mercedes-Benz Summer Event commercials. It isn't Diana Krall, or Norah Jones....the song was written originally in the 20's/30's by Harold Arlen and T. Koehler. It was remade by the likes of Krall, Bennett, Louis Armstrong, Peggy Lee, and Sinatra among others.
I've done Google searches, i've searched on kazaa, I e-mailed the webmaster at the mercedes site (email@example.com), and i've even gone to the source (html) code on mbusa.com on the off chance that the song and the songstress would be named ....no such luck.
I don't know what else to do....if anyone out there has any ideas or finds the answer, please let me know at firstname.lastname@example.org. thanks!