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 1999MercuryGrand MarquisLS , 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.