Going by the wife's Honda Insight, there can be many operating modes. Depending on the ambient temp, if the driver has "econ" or "normal mode" selected for the HVAC control, the state of charge of the batteries, if the computer detects you are in "stop-and-go" traffic or not, and probably a few other parameters I have left out. Probably a different list for the Saturn, but still many different modes it can run in.