The 2006 GMC Sierra 1500 Hybrid is available as a 4-door, 5-seat regular side. Starting at $26,205, the 2006 GMC Sierra 1500 Hybrid SLE1 4x2 is powered by a 5.3L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 21-mpg on the highway. The top of the line 2006GMCSierra 1500 HybridSLE2 4x4 , priced at $ 31,900 , is powered by a 5.3L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 19-mpg on the highway.