safe to use lower octane levels?

[Kirk]

Yes, if you put in 87 octane the engine might knock or ping in which case the DME will then pull timing. Only performance will suffer. HOWEVER, is not the performance of the car related to your fuel economy? I think what some others have tried to say is that even if you run the cheap gas the car may not run as well with the pulled timing and in the end your fuel economy may suffer. It may actually end up costing you MORE to run the lower octane because of this.