By choosing the Oshkosh [OSK] Joint Light Tactical Vehicle (JLTV), the Army and Marine Corps stand to save $6 billion over the life of the program, which will replace portions of their legacy Humvee fleets.

The most recent Defense Department Selected Acquisition Report (SAR), published Thursday, shows a 20 percent decrease in estimated JLTV program cost from a year ago. In December 2014, the total program cost was estimated at $30.5 billion.

The SAR reported a drop in total cost to $24.6 billion to purchase 49,099 JLTVs for the Army and 5,500 trucks for the Marine Corps.

Annual SAR reports summarize cost, schedule and performance estimates for major service-specific and joint acquisition programs and changes relative to previous reports. The JLTV estimates are published in 2011 then-year dollars comparing current calculations to those at the end of the program’s technology development (TD) phase.

Army officials were aware of the savings, but were publicly conservative about estimated savings prior to publication of the SAR. Scott Davis, who oversees JLTV as head of the Army’s Combat Support and Combat Service Support (CS&CSS) program office, just a week earlier predicted an overall program cost decrease of between 10 and 15 percent.

Per-vehicle and lifecycle cost were heavily weighted requirements in the JLTV competition, which ultimately was won by Oshkosh in mid-2015. The Army consistently asked for a unit cost of $250,000 or less. Oshkosh has not published the per-unit cost of its JLTV, but company officials have said their truck undershot the mark.

The program received an approved cost estimate when it began the engineering and manufacturing development (EMD) phase. That estimate was and will be revised at every program milestone.

Locking in Oshkosh and its vehicle allowed the program office to revise its calculations down significantly, Davis said during a recent press conference. He also credited stable requirements for mature technologies and a thorough competition with incentives for contending manufacturers to drive down cost and improve reliability.

The 2015 SAR said revised unit-cost estimates alone saved $3.7 billion. Compressing the acquisition timeline by about five years – which Davis said was possible because the government could buy more vehicles faster – saved another $1.2 billion, according to the SAR.

Competing the technical data package for the vehicle reduced the program cost further by $550 million, according to the SAR. Around 115 million was saved because of a decrease in support costs, data fielding and equipment training while another $332 million was written off to inflation.

Finally, JLTV “realized program efficiencies as a result of contractor systems engineering and program management downselect” of just under $24 million, according to the SAR.