Last year I had a chance to drive an E36 M3 out on a track with 93 octane and then later the same day with ~90% 100 octane and ~10% 93 octane. Primarily, I was impressed by the additional smoothness near redline with the higher octane gas.

Earlier in the year I read that 100 octane didn't do anything for the 350Z, but due to my previous experience with the M3 I was skeptical. Today I had a chance to run a tank of ~50 100 octane Sunoco GT100 and ~50% Sunoco 94 octane in my Z with 2000 miles on the clock and I have to say that I like what I felt. I didn't notice it immediately, but a couple miles after filling up I felt better response and a willingness to rev cleanly up to redline.

What I would like to know is what have other my350Z.com members experienced with 100 octane fuel?

Long winded, but thanks for reading.

 

I believe SCC dynoed with 93 and 100, they got 4hp from it. so it certainly has merit.

its not required since the Z only has 10.3:1 compression, but as always a little extra isnt gonna hurt, dont go any farther tho, eventually the car wont fully ignite the gas and you can end up toasting your cat. thats why you dont want to run real high octane race fuel on catalytic converter equipped cars. a little octane booster wont hurt tho.

 

From experience it can actually hurt performance. Some guys use it to detect fake spark knock..but otherwise as someone else said, it wont burn off properly. Chances are the E36 M3 had some kind of spark advance issue or is a really high compression motor. At 10.7:1 I have considered trying it out, Since I don't have a cat anyways I don't have much to worry about. Let us know what you find out.

 

Octane is merely a fuel's resistance to detonation. Nothing more, nothing less. It should not damage anything (besides your wallet). For a full explanation, I shall defer you to part 3/4 of the Gasoline FAQ: http://www.faqs.org/faqs/autos/gasoline-faq/part3/

If the 350's ECU is dynamic enough to detect higher octane fuel and advance ignition timing, then you will gain power. Otherwise, using higher octane fuel w/o advancing your base ignition timing will do next to nothing.

Michael.

 

it can detect detonation, and reduce the timing, which would decrease HP, however based on the Z's not extremely high compression ratio, no one should be getting any detonation with 91 or 93 octane gas.

perhaps why there is not such great gains to be had. but maybe we are getting occasional detonation in the higher RPMs and dont even realize it. its possible, and the extra octane removes this...

I certainly dont claim to understand why a car with 10.3:1 compression would benefit from 95+octane(many cars have 11:1 or higher) but SCC had a dyno that showed it, so it cant be all bad...

 

The E36 has a 10.5:1 compression ratio, comparable to the Z. I was mostly wondering what others have actually experienced. Without knowing the operating parameters of the ECU it is hard to tell if it is running optimally with 91-93 octane. I was impressed by the BMW's ability to utilize the higher octane fuel and was curious if the 350Z ECU had the same room for improvement.

On a side note, I'm wondering if the smoothness I'm experiencing is similar to the effects of the grounding kit? A one time cost is better than $3.999 a gallon

 

Race gas (i.e., 117 octane) will burn out your cats, but on a highly tuned engine can yield 50-100hp. The best example of this is on high powered turbo engines. You can usually run much higher boost without detonation on race gas. On my 1991 300ZXTT, I had downpipes (no pre-cats), then straight dual 3 inch pipes with no cats all the way back to dual HKS mufflers. On pump gas I would run 105mph in the 1/4 mile at 15psi. On race gas (110 or 117 octane) I would run 109-110 mph at 18-19psi.

The Car and Driver issue on tuner cars featured a PFS 3 rotor RX-7 turbo. They listed the horsepower produced on pump vs race gas and the difference was staggering.

I would never run race fuel in my 350Z though. At least not until I have twin turbos and no cats!

 

You brought up a very good point. Since the Z is N/A it makes a world of difference. What most of the Supra guys fail to mention when the claim faster times with higher octane is they can turn up the boost. Otherwise unless you had some kind of detonation issue or the car wasn't pulling proper spark advance then it shouldn't give you anymore than 93 octane would.

 

The October '02 issue of SportCompactCar has one of the first road tests of the Z. In this issue they actually dyno'd a car using 91 Octane and 100 Octane. They saw a 5hp gain at the wheels using 100 Octane!

Here's the link, with pictures, dyno chart and all:

http://www.sportcompactcarweb.com/fe...san/index.html

 

how much does 100 octane run per gallon price wise at sunoco?

 

Its about $4 a gallon @ Pitstop in NJ for cam2, I think thats 98 or 100 octane... @ the track, its about $4.50 for 100 and 5.25 for 110... I put 110 octane in my racing kart, good thing I only burn 1.5 gallons for a whole day racing.....