The 2007 Cadillac STS is available as a 4-door, 5-seat sedan. Starting at $42,390, the 2007 Cadillac STS V6 RWD is powered by a 3.6L , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 27-mpg on the highway. The top of the line 2007CadillacSTSV8 AWD , priced at $ 53,360 , is powered by a 4.6L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 15-mpg in the city and 23-mpg on the highway.