I've used two tanks of gas - one filled with 100 Octane and one with 91 octane.

I went to my favorite station that sells 100 octane unleaded VP racing fuel at a specialty pump for a fill up (6.499 a gallon)

Using 100 Octane I clocked 283 miles using 13.014 gallons = 21.75 miles per gallon (13.014 * 6.499 = $84.58)

Usine 91 Octane I clocked only 255 miles using 13.6 gallons = 18.75 miles per gallon (13.6 * 4.499 = $61.20)

The SRT was just not as crisp on the 91 octane (and what ever it is they cut it with for the "summer blend")

The price difference per fill up was $23.38 - but I gained 28 miles and burned about 1/2 gallon less with the 100 octane - so it actually only cost me $14.38 more to use 100 Octane fuel.

 

Could you put in 93 octane and than add a fuel additive? Or are those additives just bs?

 

They don't sell 93 Octane at the pump in So Cal. I (and many others) could only wish.

Every independent test I have read on octane booster fuel additive is not good; especially with the fuel blend we get in Ca.

 

:-( No 93 in Ca.

 

Thats odd. I can't find 91 here in NY. Only 93 octane...

I sure can't find 100, I would love to try that. Is there a specific chain a gas stations??

 

We don't have 93 in NE Oklahoma any more. The best we have is 91, which achieves its octane rating by using corn.

Is there any disadvantange to using "Ethanol" octane-boosted gas?

 

Ethoenol burns cleaner, but it also burns quicker - you may night acheive the same gas milage.

 

There are multiple disadvantages when using ethanol as an octane booster.

First is the latent energy of combustion:

1. Ethanol: 75,700 Btu/gallon
2. Gasoline: 115,000 Btu/gallon
3. Toluene: 114,056.98 btu/gallon
4. Xylene: 115,000 btu/gallon

Less energy output = less power per unit volume.

Second is the fact that the ethanol has vastly different nernst cell O2 sensor readings for stoichiometric combustion compared to gasoline. I've seen a few posts about this, but some cars have been running badly due to bad O2 sensor readings from Ethanol/Gas blends.

I've used Toluene with considerable success. I didn't want to experiment with Xylene due to the health hazards. Other people have mentioned using commercial racegas recipes.

Ethanol is great in an E85 or E100 mix (it's not corrosive like Methanol) but unless you have a good way of dessicating the fuel, long term use is going to mean rust somewhere down the line.

 

BrianBrave,

Could the difference be the 91 octane having up to 10% ethanol, and the 100 octane having none?

 

Yes - I discovered that blending the 100 octane with pump gas that contains ethanol will have mixed results.

The 100 octane fuel is not blended with any ethanol.

Thus, It runs and performs better, plus I get increased milage

 

can you put 100 octane in any car?

 

A good read...

http://www.osbornauto.com/racing/dragster.htm

 

You've nailed it Sonoronos!
Anyways, if they're using Ethanol to boost octane then they're not actually selling "premium"! I would call this fraud, they may call it something else.

 

Their marketing department would call it "Going Green".

I know some stations have a sign on the pump stating that the gas could contain up to 10% ethanol, but is that signage required? I don't want to give business to a gas station w/ 10% ethanol simply because they were deceptive and didn't add the sign.

 

Just take the initial cost hit on an alcohol injection kit and get the boosted octane and the benefit of the cooler intake air. In the end it will come out cheaper and better for performance than 100 octane fuel.

 

It is required by the Feds., I believe.
But you don't ever actually know if Ethanol is present or not hence the "May contain" warning.
It all depends on the price of the locally produced Ethanol; if it's cheaper than gas then it's in the mix.

 

There are several reasons why, in my case, I did not install an alcohol injection kit.

Injection is the way to go for the hard core 1/4 mile racer where heat soak can cost you 3 - 6 tenths of second and the trophy at the end of the day.

BUT - My research showed that alky/meth injection only lowers IAT's by 30 -40 deg F and I've already achieved close to that with my new IC tank - (but granted, not after the fifth 1/4 mile run of the day)

While the proper meth/alky will increase the octane level - I could find no hard numbers or (R+M)/2 testing that would say "by how much". Numbers varied between websites, author and retailer.

Unless you add a big **** 2 gallon tank in the trunk - you only get about eight to ten - 1/4 mile runs. Not near enough for a road/canyon warrior like me. (bikecop could chime in here about his system) for on and off the throttle driving - and injection kit just won't work.

If you don't have knock or detontation issue - an injection kit offers very little gains. If you do - then this (or higher octane fuel) is one solution.

But most importantly - I still have close to two years left on my factory warranty - My dealer is ok with the mods I have done and has no issues with the bling - add injection kit (Alky/Meth or NOS) and I can fagetaboutit.

There were other issues like lost lubrication on cylinder walls, alky/aluminum issues , etc...

So in the end $15 - $20 more at fill up does the trick for me and provides a whole tank-full of fun no matter where I'm at. When that little ricer, or Stang pulls up next to me, gives me "the look" and rev's his engine, I don't have to roll my window down and say "I just ran out of Alky - can you help a guy out?"

 

I did a somewhat similar test...............but with different fuels and measured different parameters. I converted my 6 to E85(105 octane) and raced it at the track, then I drove the hell out of it all week and filled it up with 91pump gas and wend back to the track the following week. The temperatures(87*) were the same as were the 60' times(1.89-1.90) and I ran .3 seconds faster running E85.....................and I still haven't had the ECU tuned to take full advantage of the E85 yet.

 

I run one-third 100 with the rest "91" (in quotes because our gas is so bad here in Phoenix with the anti-smog additives) and my Xfire, with all the mod's, runs MUCH better, much smoother all the way to redline. Haven't actually checked the mileage, but I get more miles per tank for sure.....of course, 100 is $7.25 at the Scottsdale station here that carries it........

 

I used to do two tank fulls of 100 octane when im doing a track day. First tank to get ECU to adjust and second tank is for day of road racing.

I stopped doing this after the track day I did with Timelord, HDDP, and X'ed at Cal Speedway.

During a session, X'ed was behind me and when we hit the oval where you normally go WOT, he said that a big cloud of black smoke (guessing carbon build up) came out of my exhaust. I assumed this was carbon build up from running rich.

So question is, does running on higher octane on a regular basis cause your engine to run rich thus the carbon build-up?