Elmo P. Shagnasty wrote:
> In article <i_WdnbHfUslmVCPfRVn-jA@speakeasy.net>,
> jim beam <nospam@example.net> wrote:
>
>
>>>Higher octane fuel, in fact, will lead to *less* gas mileage for that
>>>car.
>>>
>>
>>not necessarily. depends how smart the engine management system is. in
>>the "old" days before knock sensors and crank angular velocity
>>measurement, igniton timing had a fixed map. with the above sensors,
>>you have a base map, but also an algorithm that monitors these two other
>>factors and from that, it can calculate in real time a set of new
>>ignition characteristics to take maximum advantage of any particular
>>fuel. i would hope that the expensive "super econo" car's management
>>would be this smart.
>
>
> No, it has no need to do any such thing. It is designed to operate on
> 86 octane fuel. It has no need to "take advantage" of anything else.
>
but formulations change between producer, by country, by state, by
season, by law, by mistake... there's plenty of reason to use smart
management, and a by-product of that is being able to run any grade gas
to best advantage.