M1 contains Rolled Homogeneous Armor plates, a variation of Chobham Armor developed by British in 1970s. Its design has depleted-uranium (DU) metal plates, ceramic blocks, and open space. Depleted Uranium - http://en.wikipedia.org/wiki/Depleted_uranium

Denser DU metal plates can withstand direct enemy impacts via chemical and mechanical processes. When the plates are penetrated, ceramic blocks absorb the massive thermal discharge, open intermeshed spacing within the plates channel hot gas along the armor perimeter, thus preventing penetration into crew compartments. Chobham Armour - en.wikipedia.org/wiki/Chobam_armour

As for the power system, gas turbine engines offer more acceleration power, but is a massive fuel hog. M1 tanks were designed during the 1970s against Soviet armor in central Europe, where logistical centers were no more than 100 miles from the frontline. But this is no longer viable in Middle Eastern operations, thus the Army should replace the gas turbine with more fuel efficient diesel engine. Gas turbine - en.wikipedia.org/wiki/Gas_turbine

Arguments against gas turbine are as follow: 1) Being a fuel hog, getting less than one mile to a gallon. Some alleged that M1 units permitted Iraq's Republican Guard armor units to escape encirclement in 1991 due to excessive refueling stops by US Army's VII Corps. Certain estimates have place fuel transport cost at $1 per gallon by sea to destination port, but $50 per gallon over land to reach the tanks in the field. Cooler M1 Engines - www.g2mil.com/abramsdiesel.htm

2) Gas turbine engines produce tremendous heat, almost four times that of a diesel engine, making it more vulnerable infra-red guided weaponry. Some also added that Abrams undermined urban warfare tactics since infantrymen cannot follow immediately behind the tank due to 1000(F) degree exhaust blasting from rear vents.

3) Its engines are expensive to manufacture, maintain, and replace. Some parties assert that 25% of Army's maintenance budget for all ground combat systems is devoted to the 8,000 Abrams in operation. To date, no other country has adopted gas turbine engine for its armor forces, most opted for diesel engines.

4) Diesel engines are heavier than gas turbine, so ammunition or fuel capacity will be sacrificed. But standardizing ground forces on diesel fuel would greatly streamline the logistical chain for tanks, trucks, humvees, etc. Gas turbine engines were originally produced by Chrysler corporation in late-1970s, allegations abound that US government ordered the Army to select this engine type to shore up the troubled finances of Chrysler as it reeled from the collapse of their domestic automobile market. Chrysler petitioned and secured a massive $1 billion bailout loan from the US government in 1979. Chrysler auto history - en.wikipedia.org/wiki/Chrysler