Re: Surprising increase in truck MPG

Kevin wrote:
> 
> jim <"sjedgingN0sp"@[EMAIL PROTECTED]
> wrote in news:1208618428_262@[EMAIL PROTECTED]
> 
> >
> >
> > Nate Nagel wrote:
> >
> >>
> >> I find that hard to believe, but I suppose it might be possible with
> >> closed-loop engine controls, a high-compression engine, and a knock
> >> sensor/spark retard *if* you were previously running on low-octane
> >> Mexican fuel.
> >
> >
> > Wake up! What you came to know as "low-octane cheap mexican fuel" 40
> > years ago was better fuel than what most cars in America have in their
> > tanks today. And yes that poor grade of fuel does  have a lot to do
> > with why ethanol improves mileage - that is correct.
> >
> >
> >
> >>  Not all vehicles have closed loop, however (basically any
> >> engine without an oxygen sensor has no means of feedback mixture
> >> control) and I just don't see any mechanism by which a less energy
> >> dense could actually produce a lower BSFC at the same power output.
> >
> > The cars tested were modern fleet cars. Double blind studies so that
> > they weren't influenced by driver's prejudices.
> >
> >
> >
> >
> >>
> >> > It is also well known
> >> > that the addition of alcohol to gasoline results in higher octane
> >> > and in more complete combustion of the fuel than gasoline alone.
> >> > Which explains why energy content calculations mean nothing.
> >>
> >> Higher octane doesn't mean squat unless you also mill the heads or
> >> otherwise increase the compression ratio.
> >
> > Or unless the fuel is really low octane without it. Most gasohol is
> > only 87 octane. the fuel would be like 84 octane without it.
> 
>   here in the midwest most ethanol gas is 89 octane. 87 octane ethanol
> is bastardized poor gas brought up to 87 octane with the ethanol octane
> increase. I have found huge differences between these two blends. the 89
> has always worked great in most stuff. the 87 can be terrible stuff and
> result in really poor milage in anything with any real compression.   KB

That's exactly right. In most places there are 3 grades of gasoline and
the octane
ratings for regular (lowest grade) aren't very exact so regular is allowed
to be as
low as 85 octane (the pump will say 87).

	If some one wants to compare ethanol blend to straight gasoline, they
should compare
87 octane straight gas to 90 octane gasohol (E10). That comparison stands
a chance of
being a fair comparison of the same gas with and without ethanol added. If
that fair
comparison is made most cars do not lose gas mileage and many gain
mileage. 

	When someone puts regular gas that is 10% ethanol they are putting a fuel
that is
ethanol mixed with 82-84 octane gasoline. If the result is a drop in
mileage it is
not because of the ethanol - it is because their car can't handle the low
grade
gasoline. If they could put straight 83 octane gas in their car they would
see a much
larger drop in mileage. The ethanol increases the mileage the 83 octane is
what
causes the decrease in mileage.

-jim


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