The 2004 Mercury Grand Marquis is available as a 4-door, 5-seat sedan. Starting at $24,370, the 2004 Mercury Grand Marquis GS (100B) is powered by a 4.6L, 8-cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 25-mpg on the highway. The top of the line 2004 Mercury Grand Marquis LS Ultimate (230A), priced at $30,725, is powered by a 4.6L, 8-cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 25-mpg on the highway.