The 2004 Buick Regal is available as a 4-door, 5-seat sedan. Starting at $24,530, the 2004 Buick Regal LS 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 2004 Buick Regal GS, priced at $28,980, 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.