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Originally Posted by KBerryhill
The Highlander owner's manual states "For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher is recommended." It certainly does save us money, since the gas mileage has improved more than enough to recoup the extra 10 cents per gallon for 89 octane (haven't tried 91 yet, since we want to experiment with the 89 for a few tanks). And I never said it gave us more horsepower, nor did I say anything about energy. It is simply more efficient than 87 octane in our experience. Using higher octane than your engine is designed for doesn't give any benefit, and can cause excess emissions. However, the Highlander is designed for the higher octane, and therefore gets improved performance (as we've seen with ours in the real world).
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here's the thing, and i'm not 100% sure of this, but you'll note that the advertised 0-60 times specifically state that they were obtained using 93oct. i'm not sure about the 268hp but i'm guessing that was made on 93 as well. what that means is that 93 oct DOES give a hp improvement somewhere in the power curve for this particular vehicle. (i'm in agreement that higher oct does not equal better performance in most cars). the most obvious way is that the ecu is adapting to the higher octane to advance timing. all things being equal, advanced timing = more power. maybe someone w/additional info can clarify...
*EDIT - the specs on the manual do state that the hp (208) & tq (212) were obtained using the 'recommended 93 oct & that performance figures will decrease with a lesser oct. so 'performance' in this context most definitely refers to 'power'.