Ok, so I was wondering, in my neck of the woods, we have QuickTrip's
with "guaranteed gasoline" which is 91 Octane. We also have shell with
their "V-Power" and Exxon/Mobil's Super, both of which are 93 Octane. I
personally have not tried the difference of running my car on both of
these options, I ALWAYS buy 93, but once I was forced to buy 87, and I
have heard they can run it, but the stock ECM will detune to accomodate
the lower grade. I am wondering, if this +2 Octane even makes a
difference in modern multi point fuel injected engines; namely my LT-1
powerplant. Can any power gains be had from buying 93 over 91, or even
adding octane booster to my 93? Any thoughts or words of experience?

The Freak

Octane does not increase an engine's power. Rather, engines with higher
compression (thus, more powerful) require higher octane gas in order to
prevent detonation and preignition. With computer controlled engines you
will notice a decrease in power with low octane due to the knocking
(preignition / detonation). The octane rating of a fuel is a measurement of
its ability to resist detonation and preignition and has nothing to do with
how many ponies can be generated by a certain amount of fuel. Power is
determined by the temperature change when the fuel lights off, the hotter it
burns the more the hot gasses expand and the more pressure it exerts on the
pistons.

With octane, if the car does great on 91, no detonation or preignition, then
93 won't help. If you notice the 93 gets you better performance, then 91
wasn't good enough and was probably kicking in the knock sensor. If you are
ever forced to use the 87 again I would buy just enough to get to another
station and then fill with higher octane. I would also stay off the peddle.
The control module can compensate for some of the preigniton / detonation
but maybe not all of it. The end result of too much of too much knocking is
melted pistons, the higher the revs the more susceptible the engine.


"FBodyFreak" <xavierkoenig (AT) gmail (DOT) com> wrote

Ken wrote:

In a nut shell, use just enough octane to keep the engine from pinging.
Any extra is just a waste of money.

Here's what you should really be concerned with:

http://www.toptiergas.com/

Patrick

NoOption5L (AT) aol (DOT) com wrote:
octane the engine was designed for. This should normally allow you to
get performance without detonation WITHOUT needing to retard the timing.

--
Cy Welch
89 Camaro RS 5.0 TBI
98 Passport
03 Malibu

I notice a big difference in gas mileage and performance. Maybe I'm just
sensitive that way but I only use 92-93 octane. You gotta feed the
beast.!!!!


-CCC

It's best to set the spark curve and time the engine with the lowest
octane fuel that won't pre-ignite under load. Even though there's
absolutely no difference between gasoline's potential energy based on
octane; the resistance to ignition (octane) affects combustion timing
without changing spark timing. There's a lot more to it (waaay lot more)
but we can try something else.
Maybe somebody here can do a simple study. Let somebody else fill your
tank without telling you what grade fuel it is and, then, you make one-line
notes about your experience.
Should be the same person, same gas station, same driving conditions over
several tanks. Use each tank down as close to "E" as you comfortably can
and then fill up again with a secret octane. My sit. won't let me do that
right now but would be interested to see outcome. Heck, even throw in some
93. Might be surprised by the perceivable difference in drivability and
mileage or lack thereof.
Regards,
Drink

"Camaro Cowboy" <coolcamarocowboy (AT) webtv (DOT) net> wrote

James Drinkwater wrote:
A item often over looked in octane debates/questions on recommendation
is: Not all gas is the same.

The rating method in the USA is RM2. Gasolines meet the Minimum
required mathematical formula for the rating they are given. Some may
Exceed that rating. An Example is shells V-power. In the part of the
country Im in it will be anywhere from 93 to 95 Octane, and possible as
high as 97 Octane. That's according to a pamphlet shell put out at the
filling stations last year. While it would be fine and dandy to use in
Electronic Fuel Injected vehicles that map out the best fuel and spark
curves off the sensor info, trying to tune in a High Performance
Carburated car on something with that much swing would be impossible.

My favorite fuel is being phased out around here, that is Sunoco Ultra
94 Octane. Which is what I tuned all my Performance V8's for.

A question that I always get asked is: what should I run in my car?
Although with todays fuel prices that question has been replaced with:
whats cheep and safe?

I always recommend to my customers with stock vehicles to find a good
gas station, and stick with it. Do not go lower then the recommend
minimum octane for their cars (usually 87 or 89), and that it never
hurts to use higher rated fuels. The premium fuels usually have the
better additives, such as fuel system cleaners, while the lower octanes
don't.

In the end does it matter? Yes. From what I have seen the people that
spend the extra on premium fuels have less injector failure, less issues
with clogged injectors, less carbon build up issues, less over all fuel
systems issues. It's always the customer that run the cheep crud that
come in with fouled plugs, carboned up EGR systems, and clogged or bad
injectors. They are also the same customers that won't listen to me
about adding a can of fuel system cleaner to their tank with a fill up
every X number of miles.

As for Camaro Cowboys car, does it need the premium fuel, maybe not. Is
he hurting it? Not at all. Is he wasting his money, no not really. If
you can afford it, with out a major effect on your budget, go for it.
Charles

I had a 96 T/A for a few years and recently came across a deal on a
99. When I had the 96, I only ran 91 octane or higer. Once my
girlfriend took the car out and put gas in it while she was out. I
noticed an immediate difference. The car was a six speed and taking
off with the lower octane was not as easy. It wanted to stall out
when letting the clutch out. The 91 never gave me that problem. The
gas mileage was better with the 91 too. I have not tried changing the
type of gas I use on the LS1 motor yet, but I expect similar results.

On Sat, 28 Oct 2006 15:51:13 GMT, Charles Bendig
<rarepartshunter (AT) yahoo (DOT) com> wrote: