The 2006 Buick LaCrosse is available as a 4-door, 5-seat sedan. Starting at $21,830, the 2006 Buick LaCrosse CX 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 30-mpg on the highway. The top of the line 2006BuickLaCrosseCXS , priced at $ 27,330 , is powered by a 3.6L , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 19-mpg in the city and 27-mpg on the highway.