On orders from Congress, the U.S. Army will review whether it makes sense to upgrade the M1 Abrams tank engine with a more fuel-efficient design.

The Army has about 6,000 Abrams, the service’s main battle tank made by Falls Church, Va.-based General Dynamics Corp. Thousands of the hulking vehicles, each weighing about 70 tons, sit idle at a depot in southern California.

Army Chief of Staff Gen. Raymond Odierno last year testified that the service has plenty of tanks to respond to any global contingency and asked for permission to temporarily stop buying newly refurbished versions to fund other priorities, such as helicopters and other vehicles being heavily used in Afghanistan.

Lawmakers denied the request. Now, they’re giving the service $90 million it didn’t want for the so-called upgrade program, according to a copy of the recently approved 2014 National Defense Authorization Act, which sets policy and spending targets for the fiscal year that began Oct. 1.

The tank funding “that the Pentagon hasn’t even requested” is an example of the way in which the legislation “is out of touch with reality,” William Hartung, an author and director of the Arms & Security Project at Center for International Policy, a research organization based in Washington, D.C., said in a statement.

The bill, noting the Army and Marine Corps don’t plan to replace M1A1 or M1A2 versions of the tank, calls for the services to consider replacing “the current engine with a modern, fuel efficient power train.”

It directs Army Secretary John McHugh and Navy Secretary Ray Mabus to submit a report to the congressional defense committees by June 1 “on a business case analysis and an investment strategy” to add a modern fuel-efficient engine and transmission for the M1, according to a copy of the legislation.