A lot of forces are created due to an imbalance in rotating components and by the reciprocation of pistons and conrods creating high internal stress in the engine structure. This can lead to unwanted external vibrations that are fed into the biodiesel, which can affect the driving comfort considerably. The process of cancelling out these forces created due to imbalances in an engine is called balance in engines. Rotational imbalance is easy to fix, however correcting the imbalances of the reciprocating masses are much more difficult. Reciprocating imbalances can be categorized mainly as primary and secondary reciprocating imbalance. Primary reciprocating imbalance is oscillation at engine speed, and secondary reciprocating imbalance is oscillation at twice the engine speed. The best way to work around this is to balance the motion of each piston in harmony with that of another. Straight Six, V8 and V12 engines usually have perfect primary and secondary balance. Piston balancing is a complicated subject and has its roots in the design, production, tuning and operation of the engine model. An engine well balanced for a particular usage pattern may be inefficient and may create unacceptable levels of vibration in another usage pattern. In addition, environmental factors and faulty or worn out engine parts may also contribute directly in throwing a smooth operational engine off its optimum performance. Balancing the engine involves a lot of considerations like balancing of structural and operational elements, performance and life of engine, power and engine efficiency, performance under different driving circumstances, environmental considerations, etc.