That rule does not apply if you have a car with forced induction. They have a lower compression ratio because they add boost. The higher the octane the better. (Assuming your air / fuel ratio is dialed in properly) In fact, insufficient or low octane can cause detonation, and then you can go BOOM!

This is very true. I should of said with normal air intake. My bad:(

Im in the same boat my 2013 Camaro 2SS with headers is tuned for 91 octane. Even then the Camaro states in the manual for V8's that 91 minimum is recommended.

I use 93 + meth injection in my STI, just 93 in my WRX DD.

Yes.


tune + turbo = knock or downregulated boost without high octane

You're good - you said "generally speaking" and most cars do not have forced induction. I wasn't correcting your statement, I was just letting folks who didn't know, like maybe the OP, that the general rule doesn't apply to forced induction cars. Having said that, you "can" run them on lower octane, BUT I don't know why anyone would want to because they don't run well at all and you should NEVER, UNDER ANY CIRCUMSTANCES, romp on them because BAD things can easily happen at high boost and low octane.

Only thing I use premium in is my Road King.

I don't use higher octane gas unless the car requires it (generally speaking, higher performance motors) but I do try and use non ethanol gas. Many gas stations offer non ethanol gas as an option and it's about $0.30 higher per gallon but IMHO it's better for the car and I get better gas mileage when I use it.

I have to. Turbo'd car.

Yes. You should all buy premium fuel, regardless of what your vehicle's manual recommends.

Understandable. Don't they come with some type of knock sensor that will pull timing in case someone goes full reerun and / or accidently fills up with regular 85/86/87 octane?

I could be wrong, but I was under the impression that modern cars will reerun the ignition timing to prevent pre-ignition. If so, you don't have to use premium, but the vehicle's performance will suffer.

I have always heard that higher octane will allow your engine to run more efficiently thus allowing your tank of gas to last longer. Is this not true? FWIW when I run 91 out here in the high altitude my tank will last 3-5days longer until I have to fill up again as opposed to 85 which is like "crap through a goose" it seems.

I've been told this too and I do think this is true, that is, motors run better on higher octane fuel, especially the smaller and higher reving engines. That being said, I'd like y'all's opinion on this issue:

If you only had one choice--either put high octane fuel in your car OR non ethanol fuel (87 octane) in your car, which would you choose? Ideally, you COULD have both, but it'd be real expensive gas. So, if you can only choose one of the two options, which way would you go?