100 octane
 

I'm looking into running 100 octane. I've heard that our cars respond much better to it. I've heard the hype about the supposed 100 octane tune. This isn't about that. What kind of fuels are guys running that race on the road course? Has anyone dyno'd to see a difference or watched the timing tables with and without it? I know weapon x has sold pulleys to some people here. What fuel are they running?

GM calibrates for 93-oct fuel. Running straight 100 unleaded is probably a waste of money. If you are concerned, what I'd do is mix 100 unleaded with the appropriate amount of pump gas (either 91 or 93, depending on where you are buying fuel) to get 94.5-95-oct. That should do, even on warm days.

I just did Ron Fellows Spring Mountain ZR1 owners school Jan 25 and 26. I inquired about what fuel they use. Its 100 octane. I was told they use it because otherwise only 91 octane is available to them. They say all their ZR1’s are 100% factory stock (without optional “Jake” air filter system).

In Spring Mountain's case, it likely makes more sense to use straight 100-unleaded. With as many cars as they have and the need to streamline maintenance, mixing fuel would be a PIA. Besides, maybe they have a fuel sponsor.

Is this done for a safety reason? (Engine life)

The engine is supposed to get at least 93 octane. It has knock sensors and if the octane isn’t high enough, ignition happens too early and the sensors retard the timing to prevent damage but performance is affected. There are other things going on as well, but that is a simplistic explanation.

I have 93 and 100 octane tunes in my tts, huge difference in a tuned turbo stage 4 car, 72 whp difference from 93 to 100, have not seen any advantage to using 100 in a stock tune ZR1, save your money until a tune is available. :)

I always track 100 I tried a tank of Sunocco 93 at Daytona and did see some timing being taken away. Density altitude and temps will be other factors. I just returned from Spring Mountain 2700 foot or so above sea level and they run 100 as well.

100 oct will deter knock events, considering all the mentioned above variables to track conditions. Definitely worthwhile, use it.

There was no power difference seen during our testing and timing did not change with its use.

Thank you all. It sounds like 100 on the track for sure and on the street it will vary but being in California I’m stuck with 91.

There will be gains over CA 91 even on a stock tune. Good 93 would allow a good bit more timing on the factory tune then CA 91. So given the option I would definitely run 100 octane unleaded with a stoich point around 14.1 on the track for best performance and safety.

I wonder if the 93 is for sea level evaluation but I know for a first hand fact, in the mountains at 5,000’ and up, lower octane pings just like like too low of an octane at sea evaluation. But getting a 93 octane in the mountains isn’t always easy. So at Walmart I get octane boost by Gumout that’s about 3 bucks per bottle and treats about 15 gallons. I carry this with me on any trip as a CYA item and it works well enough.

Add a 32oz. Can of Boostane professional to a tank of 93 and it will be 101 octane. You can add more timing to take advantage of the added octane but as far as i know you still cant tune a ZR1 as of yet.

Don't waste your money buying the auto parts store/Walmart octane booster, those are a joke.

Appreciate this thread, as I'm in CA + we can routinely only get 91 octane max.
I've read/heard that octane booster used regularly can "poison" the catalytic convertors?
Does anyone know if CA-designated/build-coded ZR1s "tuned" for 91 octane? Lesser hp/torque?
Thanks in advance!

I believe that related to the “poison” catalytic converters issue is the “new” dexos 2 0w-40 ESP Mobil 1. If you go to Mobil’s site and compare additives like ZINC, you will find the ESP oil has less than other oils previously recommended. The name itself tells us it is “emission” minded. It might be the main reason NOT to just run 15W-50 all the time even in warmer climates instead of using it ONLY for track days. (IMO)

Hi Rinaldo!
Thanks have appreciated your many helpful posts!
Yes, I heard this too on other Forum posts...
I was also wondering about gasoline "octane improvers" + their impact on the cats. And what, if any, CA cars might have "special tuning" from the factory specifically for 91 octane gas.
Thanks much!

Im pretty confident all of them have the same tune. A majority of them now meet California emissions (50 state) and its not worth the time to have different software. I bought mine from Florida and like many here had it shipped over and gm can’t predict such a thing.

If you live in socal you can get 101 in Newport Beach at the 76 station in Newport Hills. 2 gallons per tank makes a heck of a difference in my 82, not so much in the 2013 ZR1

Hi All,

Found this website that can help you find 93 octane gas in your area: http://find93.com .
Hope it helps, good luck!

What about adding a gallon or two of e85 to your 91, what’s the effect?