The real reason why we should be using premium is because of the compression ratio, or CR, which is > 10:1, and the newer they get, the higher the compression ratio. The number that is reference on the pump is the octane rating, not news, I know. In leman's terms, octane is the resistance to detonation. So let's say you take a mid 90's 350 Chevy, it's going to be 9.0:1 compression ratio. It will squeeze the volume in the cylinder 9x smaller from where it starts at bottom dead center, or BDC to TDC. What is important about this is that this is where detonation come into play. The Chevy engine will call for 87 octane, because the more volatile gas, 87 octane will not effectively compress more than (IIRC) 10:1 CR. If you were to use premium in the Chevy engine, you wouldn't notice one bit because the extra resistance to detonation isn't required. Now, for the Lexus V8, which I believe are all at least 10:1 CR, and with VVT-i, it's even more important as the compression ratio will change per firing cycle. If you were to run 87 octane in a UZ V8, the electronics will take care of any real issues with spark timing and fuel trim, so you'll never notice the difference. However, what you don't see is that the 87 octane fuel is actually combusting before the piston reaches TDC, because the fuel to volatile to handle the added pressures of high compression ratios. Likewise, race cars often using ethanol based fuels because they have higher octane ratings, which give them the ability to make more power, while reducing detonation, knocking, and ultimately failure.

I Forgot who Posted this on another Thread but i still give many thanks to that person!!