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