Re: Toyota Avalon - what grade of fuel?

You are correct, over the years many small 4cy Japanese engines were
designed to run on higher octanes as they were spun up, so that they could
advertise higher HP figures. Unfortunately spinning up an engine to gain
HP also lowers the torque curve relationship, separating the torque and HP
curves results in cars equipped with an automatic tranny being a slug when
one needs that torque to get going and maintain speed on grades. The 4cy
in a Camry is a prime example

Modern microprocessors can easily de-tune an engine by adjusting the F/A
ratio and timing to run on a lower octane fuel that for which it was
designed, however it will not run as efficiently as it will if run on the
fuel for which it was designed. When an oil company implies your car will
run better or premium fuel, they are not being disingenuous because they are
not referring to all cars, rather those designed to run on premium, not
running your 89 octane car one 93 octane

Engines designed for higher octane's can easily run satisfactorily on 87
octane fuel. Modern microprocessors can do-tune to compensate for fuels
with an octane rating lower than the 93 or 91 octane rating for which the
engine was designed to be the most efficient, as long as the result does not
cause excess pollution. At that point the check engine light might
eliminate as the O2 sensor detects insufficient O2 content. The
microprocessor does the same to run on engines that use 89 octane gasoline's
when fueled with gasoline's that contains up to 15% ethanol but the result
is fewer MPGs



.. "Jeff" <kidsdoc2000@xxxxxxxxxxx> wrote in message
news:s6iCj.21673$Qy3.21653@xxxxxxxxxxx

Elmo P. Shagnasty wrote:
In article <6rhCj.8679$hr3.5430@trnddc04>,
"Jeff Strickland" <crwlr@xxxxxxxxxxx> wrote:

You mean, the requirement that was written by marketing people so as to
make sure the buyer knows that it must be a "premium" car because it
requires "premium" fuel?

No, the requirement that was written because the machinery "needs" it.

At one point, Lexus made sure to point out that use of lower octane fuel
would not damage the engine.

Then one year, they took that out.

Trust me, use of lower octane fuel will not damage the engine. The car
doesn't NEED it. Marketing NEEDS it, because stupid buyers think that
higher octane fuel is "premium". And of course a "premium" car would
naturally require "premium" fuel, right?

Even though the base engine is sold in millions of Camrys.

It also lets them advertise a higher horsepower and torque spec.

Jeff


.

Relevant Pages

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    ... The cetane rating of gasoline is so low that, if you can ignite it at all ... time it takes for fuel ignited at high temperature and compression to ... An octane rating, which is very low in diesel and much higher in gasoline, ... and the later is the heat release in the HCCI engine at a given condition. ...
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