The real problem occure when low octane causes the car to pre-ignite. In this case the piston is still moving up when the charge ignites causing the force of the piston going up to slam into the shock wave of the gas ignition. This is horrible.. especially on a supercharged or turbocharged car. Burns rings, bends valves, etc.. lot of force at work. I run about 12 lb of boost in my other car and will only run supper coupled with a boost sensitive ignition retard. I've spend time on a dyno optimizing timing, fuel, and boost so I know under what condition I can run what octane. Sometimes I need race gas.

As the article states, a knock sensor will delay when the spark fires possibly reducing power and mileage. While that is true, I have not noticed any seat of the pants difference... my seat is not very sensitive.. my X5 is slow (even on premium) since it is 4700 lb and 225 HP and my Mustang is fast since it is 3400 lb and 475 HP.. I have a hard time noticing a little hp loss on the X5 with those two reference points. My my real question was does anyone notice knock with regular gas. Sounds like the answer is no and it is safe to give regular a try. I'll likely still run premium from time to time (hot weather) but not always.