The engine ( as almost every new car) is equipped w/ a knock sensor. The SC has a pretty low compression ratio so use of lower octane ratings is okay even with timing pushed. However, unless you are using a ecm chip for performance, adjusting the timing may have little effect as the other sensors in the ecm system will make a compensation for what the stock chip recognizes as out of the ordinary state of tune. You most likely will not hurt any thing but may make the engine performance suffer at different areas (low end torque, economy and emmisions) Unless you have a programmable eprom chip or access to a dyno, I really see no advantage in meesingwith the timing of a modern vehicle.