Does 100 octane fuel serve any purpose?

[KellerRacing]

For a daily driver, I mean...or at least a car that has been set up to run on, say, 93-94 octane fuel.

There's a Shell about a mile or two from my home that sells 100 octane fuel right there at the pump alongside the cheaper stuff, and it reminded me of how good exhausted AvGas or CAM2 (at least, that's what I think it was called) smelled at the track.

Then I saw the price...$5.99/gallon. WOW!

So, is there any logical reason that one would plunk down $120 to fill up their 20-gallon fuel cell?

Paul

[sharpe 1]

Just the smell.

[Yetiman]

For a daily driver, I mean...or at least a car that has been set up to run on, say, 93-94 octane fuel.


In that case, no, there's no advantage.

BUT, if you were to use the higher octane fuel you could run more ignition advance and potentially make more power. but it depends on your engine build. If you have a fairly tame motor to begin with and have relatively low compression etc. there will be little or no advantage to be gained.

If however you have a much more stout engine build, and are cranking the timing back in order to be able to run on pump gas (and the motor is showing signs of not liking it) then there is a lot to be gained.

Around here the 100 octane race gas is the unleaded stuff, and there is also 110 octane leaded available.

Do not run the leaded stuff if you have catalytic converters or an oxygen sensor or you will ruin them almost immediately.

My motor was built around 93 octane gas, and there is very little to gain from race gas (except in very hot weather when the engine is more prone to detonation and I mix some in for added protection).

I have a nitrous setup on though, and the few times I have used it I was running race gas as a safety margin against detonation.

[KellerRacing]

Originally Posted by Yetiman

Life all comes down to a few moments. This is one of them!

One of my all-time favorite quotes from one of my all-time favorite movies!

[Jeff Frigo]

Originally Posted by Yetiman

Do not run the leaded stuff if you have catalytic converters or an oxygen sensor or you will ruin them almost immediately.

What is a catalytic converter?

[DAVID GAGNARD]

Jeff;

It's kinda like a "cadillac converter", only smaller.......

David

[SCOBRAC]

It would make slightly more power, but for the cost you wouldn't see a great improvement. Where octane makes a difference is when you run so close to the maximum operational limits of a machine, not running it would do damage. Examples are in an airplane that needs to extract the greatest possible power from the smallest lightest possible package.

Cars are (were) like this to a point. Maximum performance meant maximum compression or the ability to compress as much air / fuel into a single space. That typically meant taking 12, 13 or even 14 times the volume of a space, in this case an engine cylinder and compressing it into the combustion chamber... e.g. 12:1 13:1 14:1 compression. Doing this creates extreme stress and friction, and heat. This heat and the rate or amount or timing (how you fire the mixture) caused things like pre-ignition, a condition in which fuel mixture ignited before the spark sets it off or detonation a condition where the mixture fired at an the wrong time or continued to ignite after the spark plug fired.

High octane fuel does two things. It has more energy available to harness the increased compression as well as ingredients and inhibitors which cause the fuel to be more stable at higher flash points and decrease pre-ignition and detonation. Modern electronics and engine management do this for you to a point making "high octane" fuel less of a requirement for a modern car. Even high performance cars will retard the timing automatically if detonation (pinging) is detected without you knowing it is happening.

If you want to try 100 octane fuel go get a gallon of Xylene from Home Depot. It will be in the paint department. Put it in your car when you have about 5 gallons of 92-93 octane gasoline. 5 gallons of gas and a gallon of Xylene is a blend yielding 97 octane. 6 gallons of 93 and 2 gallons of Xylene yields you 98 octane.

Xylene is 114 octane by itself but it's use should be limited. Concentrations over 20% will shorten the lives of your rubber gas lines, carb seals etc.

[dlowman]

octane def can help alot if you have the supporting mods. But you have to tune for it to get the advantages. Especially on the newer cars. For instance.. I have an 04 Sti that is built up. I can only get about 420 whp (to the wheels) on 93 octane. But you throw race gas in there and I can get 616 Whp. I couldnt afford all that race gas so I went 93 octane with methanol being injected right before the throttle body. Which basically is like running 104 octane or so. That gives me about 592 hp to the wheels.
Dan

[Bob In Ct]

Don't waste your money on octane you don't need.

Bob

[wtm442]

Higher octane gas is only needed if your engine pings/knocks. Other than that, its a waste of $$$$

[Yetiman]

Originally Posted by KellerRacing

One of my all-time favorite quotes from one of my all-time favorite movies!

Gordon Gekko was the man !

[chuckbrandt]

I put in 5 gallons of 100 per tank in the winter. I had a real problem with heat soak boiling the fuel in the carburetor, mixing in the 100 solved the problem entirely.

Chuck

[HI Cobra]

For grins I put about 2 gallons of 110 Avgas in with about 15 gallons of 92,
(that's as good as it gets here) and besides having it smell better it did add
a bit of power. Didn't expect much, but it was only $4.50, 92 is $3.00, so
for $3 more it was cheaper than trying the "octane boosters". I don't do it
all the time because the type of driving here doesn't justify it, but every
once in a while, why not! Nothing like a little bump for fun.

[patrija]

Where's that gas station in Alpharetta? Thanks!

[KellerRacing]

http://inbx.us/cobra/shell.html
(two photos from the pump, poor cell-phone quality)

Crabapple Shell
12690 Crabapple Rd, Alpharetta, GA 30004
(770) 664-2248

[Jbb]

I would agree if its a street car...build to run 93.....unless you dont mind paying for the good smell..

On the boats I have ....I have run many gallons of 93 thu a blown 502 running 6lbs of boost @30 degrees of timing ...locked.....The static cr when I started was 8:1 ....I ran that boat for over 100 hrs with no problems....and boat engines work a lot harder than any Cobra engine ever will.....

The new boat I have has a blown 468 with a static cr of 8:1 ...runs a bit more timing and has 12 lbs boost......I just bought fuel for it tonight and VP110...was $6.95 a gallon......

If you wanna go fast....ya gotta pay....

[mzhun]

I use Xylene but it is 20 bucks a gallon thanks to the meth labs and you get put on a govt. watch list!