The 2018 redesigned S4 is now based on the new A4 platform. This high-performance AWD sedan is powered by a 354-hp, 3.0-liter turbo V6 mated to an eight-speed automatic, the same powertrain that is on the 2018 S5. Advanced safety and infotainment systems are all up to date. The outgoing S4 is very impressive on a track, particularly in sport mode. It employs a system that splits torque from the front to rear and side to side to improve handling. The interior is well-finished and nicely appointed, with comfortable and supportive leather sport seats.