> In article <3F4BA46C.D570F06B@lycos.com>, MikeHunt@lycos.com wrote:
>
> >All of the gasoline's sold in your area are basically the SAME
> >blend no matter which brand you choose to use. Federal
> >regulations set the mix for your area, as for all others in the
> >US, based on altitude, ambient temperature among other
> >parameters. Any difference in fuel mileage is statistically
> >immeasurable even if commercials imply that it can be measured
>
> They generally all come from the same distributer, with different
> detergent packages added when the trucks are loaded.

Well, depends on your definition of "basically". While most of the
gasolines in my area contain 10% alcohol, there is one station in town that
offers pure gasoline, without the alcohol (Marathon). I suspect Shell is
doing the same thing, since their pumps don't disclose the alcohol dilution
like the others. The energy content of gasoline is higher than alcohol, so
a difference in fuel efficiency in this case could likely be measured by the
average consumer.

In the days of carbureted engines, 10% gasohol made the engine run
noticeably leaner and less strong than pure gas. Nowadays, with oxygen
sensors and feedback loops maintaining a constant fuel-air ratio, this
effect can not easily be detected.