iLLuSiON38

I recently found a 76 gas station in SoCal with 100 octane gas, at a ridiculous $9.39 a gallon. For comparison, 91 was $3.09 at the same station.

Anyhow I saw another thread on the forum about gas grades and thought I'd ask if anyone has mixed 100 octane with 91? And if it made any noticeable difference?

I'm going to try mixing a 50/50 blend of 100 octane and 91 just for the heck of it. Not going to do it regularly, just to try it out.

Calif Vetteman

I have done the mix in my 93 LT1, and my 03 LS1. Really didn't notice any difference, other than I knew I had 100 octane instead of 91.

There used to be a 76 in Thousand Oaks that had 100 octane at the pump, but they no longer have it.
Where was the 76 that you found ?

Jacked

iLLuSiON38

That's what I thought too. Will give it a try this weekend since I'll be in the area anyway.

It's a 76 station in south Pasadena. The address is 155 East Glenarm, Pasadena CA.

HalfMoon

Unless you're tuned for it you really won't see any difference. You could use one of the online octane mix calculators to get 93/94 octane instead of our 91 and see if you feel anything, but it's unlikely as it's just a few HP.

In my last Turbo car the tune I had was selectable between 91, 93 and 100 octane tunes on the fly (just restart the car) and I used to use the calculator to run 94 and sometimes straight 100 octane. With the right tune, there is power that can be had, but the factory tune is set to run conservative.

My guess is you'll do it once and then not want to do the extra cost of the fill-ups with the results in a stock car.

SRQStingray

Why, it's a waste of money.

Steve_R

Pretty much. You won't notice or feel any difference, nor is it any better for the engine.

fdxpilot

While the ECU will will switch to the low octane map and pull timing if it detects knock, there is no special high octane map if you use more than the required premium 91/93 octane gas.

Corgidog1

I would have loved to put in 100 octane in the 68 big block I once had. It would have made a diffeence as the engine was made for it-well sort of as those engines back then used leaded gas.

mjw930

It's an absolute waste of money and in most instances it will actually reduce overall performance as the high octane fuel has the potential to cause the ECM to go into a protected mode. The ECM expects to see detonation, even with the recommended octane rating. If, over time it doesn't detect any it may assume the knock sensors are defective and go into the low octane map. I know this used to be the case a few years ago but I'm not fully up to speed on the algorithms in the newer ECMs.

Bottom line, don't waste your money.

Bill17601

I worked in racing gasoline for over twenty years. There is no additional power with increased octane above the manufactures recommendations. You can increase power with high octane if your car has been tuned to take advantage of the increase. As an example higher compression. With computer controlled tune ups there is no change because the engine does not see changes that would demand high octane. When I started in gasoline NASCR used 110 octane. Now the octane ratings are less then 100. Octane itself does not increase the energy in gasoline.

Uncle Meat

Higher octane does not equal more performance in an unmodified car. It's a fallacy.

U.M.

cheapthrills

My other car is a Focus ST which is a turbo and I run an E30 mixture to increase octane. The car has been tuned for it, switchable maps on the fly from a Cobb tuner. The E30 is awesome in a tuned turbo. As others have said it's a waste unless you run a tune to take advantage of it.

Jacked

Are you guys saying a stock C7 will run just as good on 91 vs.93 octane ?

Steve_R

For the vast majority of C7 owners, yes.

Way too many people think more octane = more power. The C7 Owner's Manual calls for 91 octane, which tells you that's what the ECM is programmed for. Using higher than that will not give you more performance or any other advantage for the added cost.

Bill17601

Yes... It's like finding out there is no Santa. You can't just pour more power in modern cars. Not to mention 91 Vs 93 is not a big deal in computer tuned cars.

Jacked

I missed the 91 octane part in the manual.That would have answered my question.I know about fuels and volatility.

LT1xL82

WOW! Hang on a minute. What the heck do you mean there is no Santa?!

I just asked my mommy and she said for me to stop crying and that you're a very mean man!

Higgs Boson

If you reset the ECM it pings on 93....there is room for better fuel.

VINDIC8R

All I know is when you stop believing in Santa you receive underwear.