You can't *just* figure consumption at idle; previous operation can clog the airfilters, cutting fuel efficiency at idle by two-thirds. M1A2 range is 243 miles /391 km, figuring fuel consumption on hard surface, with fuel consumption figured at 1.83 US mi. per gal /4.3 liters per km, assuming clean air filters and fuel used in a turbine in decent condition. Fuel tank capacity of an Abrams is 498 gal/1,885 liters; more can be carried in drums or 80-gallon/300 liter rubber bladders called BRAs, which refuel the tank simply by driving over them to squeeze the fuel out. The old 5-gallon *jerrycan* is hardly worth the trrouble.
A US Army decision to switch from DF-2 diesel to the kerosene-based JP-8 (to standardize Army fuel supplies) further reduced M1 fuel efficiency. In defense of the AGT-1500, Textron Lycoming notes that all automotive engines are affected by the reduced caloric value of each gallon of the less dense JP-8, which typically means a 5% reduction in maximum range. Textron goes on to note that no changes in the AGT-1500 are required to burn JP-8, whereas diesels must adjust fuel rack and other settings or see an even greater relative drop in efficiency.
As for the AGT-1500's fuel consumption at idle, the rate is as much as 16 US gallons (60.6 liters) per hour; the official claim is approximately 10 US gal/37.9 liters per hour. The M1A2 SEP fielded with 4th Infantry division uses a newer Under Armor Auxillary Power Unit, [UAAPU] a small turbine mounted in the back deck that uses 3-5 gallons per hour. It provides enough power to run the turret hydralics at full power so the auxillary pump does not have to be used [the tank can actually engage with just the APU] and it is much more quiet than the bustlerack mounted APUs on the M1A1/M1A2s. This is more than just a matter of fuel economy though; during Desert Storm many T72 kills at night resulted from locations of enemy vehicles with thermal sights because they'd powered up engines for turret power and/or radio watches, making nice clear targets in the Abrams thermal sights. Whether developed as a part of the M1A3 upgrade or retrofitted to all Abrams [about 3000] in the US inventory, the under-armor APU is certainly going to affect fuel consumption for units not actually on the move.
Under the less-than-ideal real world conditions not encountered in the book figures the uparmored and heavier M1A2s may burn as much as 9 gallons a mile /21 liters/km with an M1 was down to 40% of its fuel after 50 mi./ 80 km). Three gallons/mile is a good ballpark figure while moving, but again a lot depends on road conditions, level or hilly terrain, fuel used and the condition of the air filters. One M1A1 had been driven 208 mi./335 km at an average speed of 35 mph/56 km/h over rough terrain before running out of fuel, working out to 2.4 US gal per mile/ 5.6 liters per km. Textron Lycoming points out that M1s operating in Desert Shield/Desert Storm were able to burn any available fuel, whether DF-2 or JP-8, without adjusting any settings and thus allowing overall demand for certain types of fuels to be met by varying the AGT- 1500's diet. Considerations of utilization of allied or captured enemy POL stocks are another advantage with the turbine-engined Abrams, though alternatives are under consideration. -archy-/-