The 1999 Pontiac Grand Prix is available as a 4-door, 5-seat sedan. Starting at $21,140, the 1999 Pontiac Grand Prix GT Coupe is powered by a 3.8L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 28-mpg on the highway. The top of the line 1999 Pontiac Grand Prix GTP Sedan, priced at $23,985, is powered by a 3.8L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 28-mpg on the highway.