Douglas Dou wrote:
> John Ings wrote:
> > On Fri, 15 Apr 2005 12:10:28 -0400, Douglas Dou
> > <douglas_dou@yahoo.com> wrote:
> >
> >
> >>I have a civic 05. My dealer told me that I could just use 87
gasoline
> >>as fuel. I followed his advice and have been using it for four
months.
> >>However, this morning when I checked the user manual, I found that
I am
> >>supposed to use 91. It amazed me since in my mind 91 is for luxury
car,
> >>which my civic apparently is not. Is there any deep reason why
Civic has
> >>to use 91? I'd appreciate if you could share me your thought.
> >
> >
> > Lately Honda seems to be engaging in a marketing ploy. Premium fuel
is
> > expensive, and people aren't inclined to buy cars that need it, so
> > trusting to the efficiency of its engine knock sensors Honda has
> > recently been recommending regular gas for some of its products
that
> > could really use premium! In those cars, the owner's manual says
use
> > regular, but premium really will get you another ten HP or so! How
do
> > you tell? Well short of a dyno test, check your compression ratio.
As
> > a rough rule of thumb (there are a lot of variables) a 9.2 to 1
> > compression ratio Integra 1.8 litre engine only needs 86 octane,
while
> > a 10 to 1 VTEC engine needs 91 octane to produce full power.
> >
> > See also http://www.tegger.com/hondafaq/faq.html#premium
> >
> >
> Thanks for the link. The link essentially says that 87 in pump
station
> is the same thing as 91 recommended in manual. Can't understand why
> Honda does not put 87 in it since the cars are sold in America.

Can you spell out what it says exactly,what type of Civic you
have, and where you're posting from? There's always been a problem
with differences in octane rating scales outside the US and Canada
(where RON is typically the pump rating) versus the US and Canada
(where (R+M)/2 - the average of two measurements) is used.

87 octane measured by (R+M)/2 is considered "regular". 91 octane
measured by (R+M)/2 is considered "premium". That 87 (R+M)/2 is
generally equivalent to 91 RON, while that 91 octane (R+M)/2 is pretty
much equivalent to 95 octane RON.

I looked it up, and Honda says the US-spec 2005 Civic Si requires
regular unleaded, but that might be a hedge that it can use it without
destroying itself. The compression ratio of the various Civics
seem to be high - from 9.5 to 9.9. The compression ratio of th
EX and HX versions is slightly higher at 9.9 than that of the Si
at 9.8.