Instead of an engine oil SAE10w, various hydraulic fluids recently have been introduced into hydraulic systems of construction equipment which generate 35 MPa and more oil pressure. An antiwear hydraulic oil VG46 became a main fluid of Japanese hydraulic excavators. A biodegradable hydraulic fluid is spreading from Central Europe to the world. A synthetic fire-resistant hydraulic fluid also became popular in the world. When those different types of hydraulic fluids were used in the construction equipment, many field pump failures were found. Thus we have investigated the various hydraulic fluids, that have caused pump failures in the field, using a Komatsu HPV35+35 pump test. The HPV35+35 test could reproduce all the field pump failures. The mechanisms of the pump failures are discussed.