The 2006 Jaguar XJ is available as a 4-door, 5-seat sedan. Starting at $61,830, the 2006 Jaguar XJ XJ8 is powered by a 4.2L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 27-mpg on the highway. The top of the line 2006JaguarXJVanden Plas , priced at $ 74,330 , is powered by a 4.2L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 27-mpg on the highway.