The 2005 Buick Park Avenue is available as a 4-door, 5-seat sedan. Starting at $35,555, the 2005 Buick Park Avenue Base is powered by a 3.8L , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 20-mpg in the city and 29-mpg on the highway. The top of the line 2005BuickPark AvenueUltra , priced at $ 40,730 , is powered by a 3.8L , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 19-mpg in the city and 28-mpg on the highway.