Quote:
Originally Posted by S Keith
That's done because lower air density means 86 at altitude is equivalent to 87 at sea level. It's a non-issue.
Unless you derived that difference scientifically, it's likely all in your head. The anti-knock agents in higher octane fuels contain less energy, i.e., Premium gas has less energy per gallon than 87. It's not a big difference, but it's there.
You're basically claiming that by burning a more expensive fuel with less energy content, you are getting better gas mileage. Unless your vehicles are adapting their compression ratio to take advantage of the higher octane fuel, which is generally not possible unless they're somehow changing stroke, bore or valve lift/duration to compensate.
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I actually did test this with my ScanGaugeII, I monitored Ignition timing and here is Link to fordcmaxhybridforum starting with Post #32 the ECM advances timing for the octane of fuel:
Bought Ethanol Free - Page 2 - General Discussion - Ford C-MAX Hybrid Forum
As you can see I gained at least 2+ mpg from going from Regular to Premium and with Octane Booster another 2mpg. Sure is nice having a ScanGaugeII to monitor ICE and HVB functions.
Paul