Kenworth announced its T270 Class 6 hybrid-electric truck at the Mid-America Trucking Show last week. The base for Kenworth's hybrid system is its Paccar PX-6 diesel engine, launched last year. This 6.7-liter engine was already designed for efficiency, giving the best power-to-weight ratio in its class. The hybrid system adds a motor/generator integrated with the transmission and a 340-volt battery pack. The electric motor combines with the diesel engine to drive the wheels at speeds below 30mph, while above that speed, it's all up to the engine. Kenworth estimates a 30 percent fuel savings during start and stop driving. Now Prius owners can get another hybrid to tow their boats or houses.