The 2003 Pontiac Bonneville is available as a 4-door, 5-seat sedan. Starting at $26,695, the 2003 Pontiac Bonneville SE is powered by a 3.8LL , 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 2003PontiacBonnevilleSSEi , priced at $ 34,020 , is powered by a 3.8LL , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 27-mpg on the highway.