As a result of the relatively high manufacturing costs of the flat-four compared to the inline-four, most manufacturers now choose the inline-four engine for economy models and have moved to inline-five or V6 engines for models requiring more power. These engines are not without balancing imperfections, but with modern computer-aided design techniques, the problems can be overcome with a variety of complex crankshaft, balance shaft, and engine mounting designs. Luxury performance car manufacturers prefer to use the inline-six, flat-six, or V8 configurations because these designs are much smoother than the flat-four, particularly at larger displacements.