Long winded, but may be of some help
I agree with DirtyOWL to point, your car will run on regular, but not as well. As a long term way to save a few bucks at the pump, I respectfully disagree.
Higher octane is required for higher performing engines. Part of that higher performance is a higher compression ratio. The compression ratio is the amount of "squeeze" created when the piston moves up in the engine, just before the spark ignites the fuel/air mixture. When you compress air, it heats up. The more you compress it, the hotter it gets. The octane controls the rate at which the fuel will burn. Too little octane = too fast a burn. Too fast a burn will result in "pinging", which is actually a mini explosion inside the engine. This will quickly result in engine damage, up to, and including, blowing holes in your piston.
The computer will compensate (partially), by retarding (delaying) the spark timing, in an effort to stop the pinging. What this does, this is where I disagree with DirtyOWL, is cause engine deposits, or what some people call "carbonizing". A carbonized engine will end up costing you more in the long run. Your engine is designed to operate within certain perameters with regards to heat, fuel ratio, etc, etc, etc, in order to stay relatvely clean internally, and operate reliably. When you start to get a build up of carbon, you can:
End up with partially blocked intake and exhaust valves. That means your engine won't be able to "breathe". Your car will run too hot, be hard to start, and require a heavier foot on the gas pedal to get moving.
Possibly (it's rare, but I've seen it) get a partially clogged injector. That will cause all kinds of problems, including leaking. More gas wasted.
Potentially set off your "Check Engine" light if you foul one the dozens of sensors that newer cars are equipped with. Then you or your mechanic has the joy of finding out exactly which one.
I feel for you, and everybody else who has to fill up with premium. My summer toy needs it, and runs like a bag of shit without it. For an every day car, you might want to try, at your own discretion, using mid grade at every second fill up. I haven't tried it, but I do know a couple of guys who swear by the practice.
