It doesn't. 

On May 3, 2013, at 2:04 PM, Rocket J Squirrel <camping.elliott@GMAIL.COM> wrote:

> I didn't know that higher octane rating = better mileage.
> 
> --
> Jack "Rocket j Squirrel" Elliott
> 1984 Westfalia, auto trans,
> Bend, Ore.
> 
> On 05/03/2013 07:12 AM, Vern in Bend wrote:
> 
>> 
>> In Oregon, all ethanol-free gasoline for vehicles is premium-grade, and the
>> cost does reflect that.
>> 
>> And, being that it is 91-92 octane, Rocky's experiment will fail to show a
>> result that can be attributed to E0 alone.
>> 
>> Regards, Vern