Abstract: Described herein is a transport tank trailer having a tank that can be used to more completely and effectively transport, store, load and unload a viscous product, such as a viscous liquid product, or liquid with solid(s) in suspension. Materials for transport, storing, loading and unloading include both food-grade and non-food grade products. Exemplary products include chocolate, paint, wastes, and asphalt. The tank system involves: a) agitation means (e.g., vibration devices) to force viscous product to flow during unloading; b) a heat-traced closed loop venting and unloading system resulting in the elimination of opening of the manhole on the tanker, which results in the release of heat; c) use of enhanced insulating materials to reduce product solidification during product discharge; and d) reduction of thermal bridges to increase product heat retention. The invention also involves an inventive cargo tank shape that promotes viscous product discharge during unloading of the tank.