The 2021 GMC Sierra 1500 is available as a 2-door, 3-seat regular side. Starting at $30,100, the 2021 GMC Sierra 1500 4x2 Regular Cab is powered by a 4.3LL , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 16-mpg in the city and 21-mpg on the highway. The top of the line 2021GMCSierra 1500Elevation w/3VL 4x4 Crew Cab 6' Box , priced at $ 47,200 , is powered by a 2.7LL , 4 - cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 21-mpg on the highway.