The U.S. Army is trying to solve one big problem it's M-1 tanks have; fuel consumption. The M-1 was notable for many innovations, and one of them was replacing the standard diesel engine with a gas turbine. This doubled fuel consumption. Thus the gallons of fuel needed to move an armored division one kilometer went from 831 to 1,356. The practical aspects of this were seen during the 1991 Gulf War, where the principal limitation on M-1 movement was not the M-1, but the fuel trucks. During that war, U.S. armored divisions used 565,000 gallons of fuel a day, and M-1s accounted for 40 percent of that. Many of the M-1's AGT-1500 engines are due for replacement, and a new design (the LV-100) that burns 36 percent less fuel. But that's still some 20 percent higher than what current diesel designs burn. The LV-100 still burns twice as much fuel when idling. On the battlefield, tanks spend a lot of time just sitting around, with the engine idling. The principal advantage of the gas turbine engine is that the tank can accelerate more quickly, which is a decided battlefield advantage.