Re: Are MPG ratings much less accurate then they used to be?

On Tue, 19 Jul 2005 17:33:43 -0400, maxpower wrote:

>
> "David" <davidbeat@xxxxxxx> wrote in message
> news:GDdDe.156426$go.138281@xxxxxxxxxxxxx
>>
>> "maxpower" <damnnickname@xxxxxxxxx> wrote in message
>> news:O4adnedb3-rJw0DfRVn-sA@xxxxxxxxxxxxxx
>> >
>> > "Percival P. Cassidy" <Nobody@xxxxxxxxxxxx> wrote in message
>> > news:pp8De.331$bG4.100@xxxxxxxxxxx
>> >> On 07/19/05 10:25 am Richard tossed the following ingredients into the
>> >> ever-growing pot of cybersoup:
>> >>
>> >> >>BTW, does the grade (or brand) of gasoline affect mpg? I sometimes
> use
>> > 89,
>> >> >>but mostly 87.
>> >>
>> >> > No, except if the motor is into serious knocking. Too much octane is
> a
>> > waste
>> >> > of money and resources.
>> >>
>> >> The Owner's Manual for our '02 300M says 87 is acceptable, but 89 is
>> >> preferable -- but doesn't say why.
>> >>
>> >> Perce
>> >
>> > If that's what the owners manual says then do not use a higher octane
>> > rated
>> > fuel. It will cause more drivability problems and leave more deposits in
>> > the
>> > combustion chamber possibly causing a pinging problem
>> > It will not improve MPG . If anything it will cause a lower MPG over a
>> > period of time.
>> > Glenn Beasley
>> > Chrysler Tech
>>
>> Don't you mean a lower octane?
> No
>
> Since when does higher octane cause more
> deposits?
>
> Since certain vehicles were designed to use it depending on the
> compression ratio. The octane rating of gasoline tells you how much the
> fuel can be compressed before it spontaneously ignites. When gas ignites by
> compression rather than because of the spark from the spark plug, it causes
> knocking in the engine. If a vehicle that is designed to use a low octane
> fuel 87-89 uses high octane fuel consistently 93+(slow burning fuel) it
> leaves deposits on the pistons, valves and so on.
> This will eventualy cause compression problems.
> Im no chemist and im sure there are people on here that may be able to
> explain it better, but i will say this, I have pulled down many heads from
> vehicles that have excessive amounts of carbon deposits on the valves ( caus
> ing lack of compression, check engine lite on) because the owners insist on
> using the wrong octane rated fuel in their vehicles, And Chrysler does not
> warranty fuel related problems either

I just checked the owners manual for my 300C and it says that use of
premium fuel is not recommended. If an engine like the 5.7L Hemi doesn't
use premium fuel what does? Are there any modern engines that need premium
fuel or are the oil companies just counting on consumer ignorance to get
an extra dime a gallon?
.

Relevant Pages

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