Not to get OT in OT, but that premise is laughable. You need to buy more expensive gas in order to get better mileage. So, it's likely a wash, no?

OP, my DD requires Premium due to it's tune, and averages 20 with the pedal on the floor half the time. :)

I use 89 in my carbureted motorcycles to avoid knocking.

Edit: IIRC Mrs. Noah's '05 Acura TL also specified 89 octane in the owner's manual. (Since sold, so I can't go check.) I think we just ran regular 87 in it, though.

if I had a car that required 89, I would use it. No point in using an octane higher than required unless you have performed some sort of tuning that requires it or there is some sort of issue (old engine, bad gas, etc.... No point in using lower than the required octane either.

I don't think you guys don't know Steve very well.
(he's mostly from the R1100S inmates SmileWavy)

Jim

A dash of diesel if you haven't got a full bladder.

my daily driver is an infiniti with Nissan's VQ motor. The book states that it runs fine on regular but for maximum performance use premium fuel. I have run it for 40k miles on mid-grade and it runs fine. I ran a few tanks of premium and didn't notice enough to justify the extra few bucks a tank.

honestly, when I bought it the dealership said don't use regular, my wife asked does it have to be premium and he was like nah, mid-grade should be fine. The lesson here is that the guy selling cars doesn't know.

The 76 around the corner from me has mid-grade with no ethanol. All my carbureted stuff gets that, T-Bird bikes and power equipment.

Todd!!! SmileWavy