Previous research by the U.S. Army defined requirements For heavy-duty diesel engine lubricants for military equipment deployed in arctic regions. These products have provided excellent performance for nearly 20 years-first as a purchase description in 1969, and fielded under specification MIL-L-46167 since 1974. Although this specification provides for use of mineral base or synthetic base oils, the performance requirements are such that only synthetic base lubricants (nominal 6 cSt) have been qualified. Consistent with the goals of minimizing the number of different qualification requirements and to field a single tactical engine oil for both year-round and worldwide use, the Army set out to determine acceptability of the arctic engine oil in nonarctic climates, Results from vehicle evaluations conducted at five outside arctic Army locations show MIL-L-46167 arctic engine oils (OEA) provide acceptable performance in diesel engines and power shift transmissions in year-round combat/tactical vehicle applications. Nonlubricant-related maintenance concerns and perceived higher cost have precluded widespread outside arctic acceptance of these products, and hence the Army has not been able to capitalize on the technological advantage and potential logistic benefits of these products.