Hino comments on B50 Engine Life Expectations
B50 calculations are done to estimate the expected life before required overhaul or replacement of engines and other rotating equipment. They are typically described in terms of 'miles of operation' in the trucking community.
B50 is the estimate of when 50% of the engines of a certain type will require major repair (repairs requiring dropping of the oil pan or removal of cylinder heads - it does not refer to rotating components attached to the engine) and is often referred to as 'average life to overhaul'. These values are indicators of the robustness of a design...
... Read more in the PDF linked below