[excelguru]

1. My car has about 10:1 compression, so I can run 92/93 octane all day long. I filled it with 100 octane and ran it without making any changes (such as timing, etc.). Did I cause any harm to the engine? Flames came from the pipes at WOT (which, I must admit, looked cool as hell - they caught it on video). But the cool video got me to thinking that maybe I was harming something. This occurred at night. The flames are invisible in the daylight.

2. Additionally, should I expect any performance increase from 100 octane since my engine isn't 12:1 or whatever? It seemed stronger, but I could have imagined it.

3. Okay... I open the valve at the bottom of my radiator to drain it. I wait for all the coolant to exit. Then if I remove the temperature sender unit at the top of the engine, I can still see a liquid level right there almost within touching distance inside the block. I can't get it to drain out any more fluid. Is this normal? Is all the coolant really drained? Did I miss a step?