The Military is interested in the development of multiseasonal extended-drain crankcase lubricants for the diesel-powered tactical fleet. Such lubricants offer potentially large savings in lubricant, logistics, and man-power costs plus they can greatly improve overall fleet readiness. To this end, a series of studies have been examining varying lubricant formulations and engine modifications to identify approaches to extended-drain intervals. Both conventional and synthetic lubricants are being evaluated for future tactical fleet applications. In addition, mechanical modifications to the engine which reduce the oil degradation rates are being studied. This paper not only outlines some of the important findings but also indicates the future direction of this activity.