The Toyota Prius has modest acceleration but has extremely high efficiency for a midsized four-door sedan: usually significantly better than 40 mpg (US) (5.9 l/100 km) is typical of brief city jaunts; 55 mpg (4.3 l/100 km) is not uncommon, especially for extended drives at modest speeds (a longer drive allows the engine to warm up fully). This is approximately twice the fuel efficiency of a similarly equipped four-door sedan with a conventional power train. Not all of the extra efficiency of the Prius is due to the HSD system: the Atkinson cycle engine itself was also designed specifically to minimize engine drag via an offset crankshaft to minimize piston drag during the power stroke, and a unique intake system to prevent drag caused by manifold vacuum ("pumping losses") versus the normal Otto cycle in most engines. Furthermore, the Atkinson cycle recovers more energy per cycle than the Otto because of its longer power stroke. The downside of the Atkinson cycle is much reduced torque, particularly at low speed; but the HSD has enormous low-speed torque available from MG2.