I have always known it pronounced 'ee-os'. If anyone understands latin, its Êôs. On a Greek web site it suggests {ee'-ahs} but I'm not sure if that helps. It translates to Dawn.
Out of interest, Eos was the godess of the Dawn. She would open the gates of heaven and lead out the sun in her golden chariot. It is also said that she had a thirst for handsome young men.
Looks like I made the right choice of car (or did it choose me).