This is old news. They have since been recalled. An ECU update and stipulation to use full synthetic Dexos 1 oil addresses the issue of low speed preignition in these engines. Basically they detuned the low end torque a little bit and slightly enriched the fuel mix.
Haven't heard of any issues with them since. The engine is also used in the new Equinox in a slightly higher state of tune than the Malibu (and frustrating transmission programming).