The 1999 Mercury Grand Marquis is available as a 4-door, 5-seat sedan. Starting at $22,415, the 1999 Mercury Grand Marquis GS 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 24-mpg on the highway. The top of the line 1999 Mercury Grand Marquis LS, priced at $24,315, 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 24-mpg on the highway.