The lubricating oils covered by this specification are military standard lubricants. The combination of engine and heavy-duty transmission requirements in this specification are not required of typical commercial diesel engine oils. They are intended for use in combat and tactical equipment including the crankcase lubrication of reciprocating compression-ignition engines, heavy-duty automatic and powershift transmissions, hydraulic systems, and non-hypoid gear units of engineer/construction and material handling equipment. Although lubricants meeting the requirements of this specification have been formulated to meet a wide range of lubricating functions, it is brought to the attention of the equipment developer the requirement to ensure that equipment, whether military unique or commercially-off-the-shelf (COTS), are compatible with military standard lubricants (see AR 70-12 and MIL-HDBK-838 for additional guidance). Monograde lubricating oils (e.g., OE/HDO-40) covered by this specification meets, at a minimum, service category API CH-4. Multigrade lubricating oil (e.g., OE/HDO-15/40) covered by this specification meet, at a minimum, service category API CI-4. Although lubricants qualified to this specification have been tested in accordance with selected Allison Transmission Inc. and Caterpillar Inc. transmission lubricant requirements, without further testing and certification, they cannot be recognized as compliant with either company's lubricant specifications (e.g., Allison Transmission TES-389, TES-439, or CAT TO-4).