I was changing the cabin air filter on Penguin LS (my son's 2012 LS MT) and noticed the KRD code on the glove box label. This engine, like the 1.4 engine in the 2012 LT, ECO, and LTZ, is also coded for 91 octane. I had tested 91 octane in his car a few years back and it does indeed run slightly better on 91 than on 87. Now I know why. It appears the Gen 1 LS engine is also being protected by sophisticated knock sensors.