All-wheel drive, a wagon body style, and more-powerful engines are 2006 additions to BMW's midsize car. AWD versions get an "x" suffix to distinguish them from rear-drive models. The lineup consists of 525i and 525xi sedans, 530i sedans, and 530xi sedans and wagons. These models have inline 6-cyl engines. For '06, 525 models swap a 184-hp 2.5-liter for a 215-hp 3.0. The 3.0 in 530 models gains 30 hp, to 255. The 550i has a 360-hp 4.8-liter V8; it replaces the 545i, which had a 325-hp 4.4 V8. The high-performance M5 has a 500-hp 5.0 V10. Transmission choices include manuals and automatics, depending on model, plus a sequential manual transmission (SMT), which is essentially a manual transmission without a clutch pedal; it can also be set to shift like an automatic. Front side airbags and front and rear head-protecting tubular side airbags are standard. Rear torso side airbags are optional. All models have BMW's iDrive, which uses a console "joystick" knob to control entertainment, navigation, communication, and climate functions. Options include a sport suspension teamed with run-flat tires, and BMW's Active Steering, which quickens steering response. Also optional are head-up instrument display, navigation system, and adaptive cruise control.