The only serious (ie approved by TACOM) engine replacement program for the M1 that I know of was the LV100-5. This was the engine developed for the XM2001 Crusader and was another 1,500 hp gas turbine with huge improvements in reliability. It did however cut idle fuel consumption down to around 18 L per hour which is only a fraction above the Leopard 2/Challenger diesel engine idle consumption. Alos road march fuel consumption would equal the efficiency (actually slightly exceed) of the Leopard 2/Challenger diesel engines. With 1,800 L in the tank compared to 1,600 and 1,200 (Challenger and Leopard 2 respectively) the M1 could out march either. But alas Ole Rummy’s cancellation of Crusader ruined this option as well as American battlefield artillery dominance.