Fuel for Track Days
 

Both tracks I’ll be at this summer(VIR & Dominion Raceway) offer Sunoco Fuels. Specifically, Sunoco 260 GTX which is 98 octane and ethanol free.

The owners manual recommends 100 octane. Has anyone used the Sunoco 98 octane? Is this suitable?

Thank you in advance!

I've been instructing st VIR for some time, and run 93 octane in my 2018 Z06.

I will be instructing there for NCM later this month as well.

You won't notice any difference running Citco 93 octane for a $1 less a gallon down the road in Semora, than what you will pay at the Sunoco North Paddock pump.

I thought they have 100 and 110 there as well, (the latter is leaded I believe).

If not, even the 98 will be overkill, but if it makes you feel good... and it smells good too :)

Greetings! The motivation for me researching the higher octane is due to some weird performance results from my last track day a few weeks ago. The car was noticeably pulling timing, particularly towards the end of the event. It was very hot that day, and the car did great with this exception.

I won’t make it to VIR for the NCM event unfortunately. I’ll be there for SCCA Track Night in July. If you’re around, I’d love to say hi!

I have run some octane "tests" with 1878. All this testing was done at near sea level in cool temperatures. I used HPTuners "VCM Scanner" application to log knock retard data during WOT runs uphill in fourth gear from 1500 to the 6600 rpm rev-limiter.

To run KR-free with that kind of air took about 96-octane fuel which I mixed using 91-oct pump gas and Rockett Brand 100-oct unleaded racing fuel.

With that in mind, I can understand why GM recommends 100-oct fuel for track use. GM makes the recommendation with tracking in hot weather in mind. On a hot day on a track doing successive laps which builds heat in the powertrain cooling systems, my guess is you'll need at least 98-oct.

Keep in mind that letting the E99s EST function control detonation with knock retard allows lower octane gas but all that knock retard makes the engine run hotter.

Bottom line: tracking in cool weather without knock retard needs about 96. Tracking in warm weather might need 98 and tracking on hot days could require 100-oct.

That's great information. Thank you!

I agree 100%. It's the hot weather that needs the high octane up to 100.

There are probably fewer than 5 people on this board who are skilled enough drivers where this minuscule performance 'hit' would effect their lap times.

For HPDE events, unless you are eeking out that last 10th in the instructor run group, you are wasting your money on $9/gallon gas.

Ask Poor-sha (Sean) or Bill Dearborn if they run 100 octane...

I've actually tried 100 octane several times and never saw a difference in lap times. I also gave up trying to bring in enough gas from off site to the track for the ZR1. At a consumption rate of 11 gallons in 20 minutes you'd need a 55 gallon drum of fuel for each day at the track.

And cold reality rears its ugly head! I like the blue car, too. :)

:iagree: Spring Mountain runs 100 octane but it is pretty hot there and the field elevation is considerable.

I would run it but not for the extra performance but to keep the engine out of knock retard for longevity sake... It's not all that much more over a weekend HDPE event to run 100 than 93 octane...

I've been using the 100 unleaded in my 16 Z06 for years. It helps for sure on those really hot days. It hasn't been a big deal for autoX, but hot laps, road course, keeps it from pulling timing.
I'm not tracking my ZR1, but if I were I would use the 100.

The only way to keep the LT5 out of detonation at WOT high rpm is to use at least 95-oct when it's cold or cool out and 98-100 if its warm or hot.

While it is true that only the most talented/experienced drivers will notice the power loss due to knock retard but, the other reason why you want to keep the engine out of detonation during sustained lapping is spark retard, makes the engine run hotter. It also degrades throttle response.

Think about it...
There are reasons the Spring Mountain people run 100-oct unleaded fuel...in spite of the fact that virtually all of its students are not the most talented and experienced drivers. Two of those reasons are reliability and durability.