My apologies Cal-cobra,

Somehow got sidetracked and did not get back to you.
Running lower octane in your SRT-6 may or may not harm the engine. depends on who you talk too. There are opinions and some with engineering backgrounds that can speak better than I.

That said, my question relates not so much to the engine but to why you would own such a vehicle, essentially a bonafide street racer, and dumb down the performance?

The milage lost by the detuned power plant would not pay for the per gallon savings. And if you're using 89 Octane an are challenged on the street, what do you do? If you're not going to answer the Hot Mustang sitting next to you barking his V/8, why buy the horsepower in the first place?

Not putting you down. Just from my perspective, why would you drive a highpowered exotic like it was a Taurus?

If you want milage, trade it for an NA. Go from 24/15 to 27/23 MPG. And do it in the same sexy body.

I can guarrantee a dozen guys here would be interested in a swap. And some gals too.

Roadster with a stick
Added rather than a repost, Check out Sonoros in "experimenting with Toluene," especially post # 78 in the technical and modification section. Good stuff.

He is always a good source.