Given proper conditions absent the externalities that would otherwise cause the ECU to pull timing (excessive heat and/or very high load), that figure can even be lower than 91-octane. However, in real-world conditions, my guess is that it's right around there where timing will not be advanced further.

I doubt they'd cripple cars for just California's sake. Yes, the cars are all sold "50 state" emissions equipped, but I'd bet money that the ECU compensates for the lower 91 octane, thus making the minimum requirement, but can handle advancing timing when the octane's higher.

Even though its not exactly a US-Spec, here's an example of what could be going on for our 370s:

Stock UK Spec EVO VII (Vishnu Performance)
EVO VII dyno run 91 vs 93 octane - NASIOC


Or for US-Spec, look no further than the 350z!
350z 91 vs. 100 octane

In the manual for the Australian version, it states: Use UNLEADED PREMIUM gasoline with an octane rating of 98 (RON)

I have alway used BP Ultimate which is 98 RON in both my 370 and S15

:iagree:
Good Post... thats the bottom line, there is need to over octane a stock car unless it's highly modified only then will you see a difference.

http://images50.fotki.com/v1557/phot...youlose-vi.gif

Seems a lot of people believe high octane = higher power.

It's been covered here and NUMEROUS places on the web that this is not the case, yet the myth still prevails.

Hmm...I should email mythbusters.

I've never ran anything under 94 octane in my life...
I love my cars so I'm gunna feed it with real food

I agree with some of the above statements. The only times I saw tat race gas helped was when the cars were modified. My s2000 loved 112 octane :D it would eat it up. I also had close to 10K worth of work done in the power department. You will know that you are gaining power when it takes the engine less time to hit redline! I ran 112 for about 2 months till I destroyed a racing test pipe from T1r... thats right I destroyed it! :tup: S2000's are known for hot exhausts but with the racing gas I cracked and disintegrated all of the welds in the test pipe it literally fell apart. I have it as a trophy in my shop and had T1r send me a brand new one saying it just fell apart one day.

But any way like others are saying if your car is not tuned to use high octane you will loose throttle response and power. I had an emanage ultimate that allowed me to adjust everything for my fuel and performance parts and I saw a good 17hp increase by going to 112 octane. Be safe with your fuel the stuff can get dangerous for you and your engine. I have 10 gallons of experimental race gas thats close to 120 octane and if you get it on you it evaporates instantaneously... some pretty cool sh1t!

YouTube - XXX Race Gas gains 14whp on stock 370z

Wow, look at how much leaner it ran with the race gas. I wonder if that is due to the way the gas is burned or if it is the ECU's doing.

At least part of it is due to the oxygenation of the gas. How much of the gain is due to oxygenation vs. high octane and/or ECU adjustment is impossible to say from this test alone. But I think it's enough to at least cast doubt on many of the positions that have been taken on this thread thus far (like the position that race fuel won't produce any gains on this car unless it's highly modified or tuned to use race fuel, for example).

Here's the original discussion thread:
http://www.the370z.com/nissan-370z-g...tock-370z.html

That's the whole problem right there.

Higher octane gas isn't better for your car...

I had some flanges welded to my S's test pipe so I could wrap it in the stock cat heat shields... it lasted about 6 months before I started hearing this ringing noise. Took me another 6 months before I tracked it down to the test pipe. when I took it off, two of the four brackets had ripped holes in the tube wall. Looks like the heat was just so bad it affected the stainless surrounding the welds. Pity.

I'd venture to say you're wrong. Many cars are actually produced in two variants for the US...the federal spec and california spec. The ECUs are modified to run on Calis piss poor gas and stricter emission requirements. Sometimes cars are sold in every state BUT California(TT Supra etc.).

Though I will agree that running higher octane then is needed will net you zero gains...in fact often times it can hurt your overall performance. Optimally you want to run the lowest octane your engine can run on without detonating as this will give you the most power and mileage. As soon as your engine detects knock it pulls back timing/adds fuel to the map to run a more conservative and safer tune to prevent future detonation.

As for the original posters question, your ECU does not read octane levels it only sees what the O2 sensors and knock sensors tell it. You can run as high of octane as you want but it would be pointless to run anymore then you need and may do more harm then good. Just run 91-94 regular pump gas...anything less and you're engine will likely run a safer tune and anything more would be a waste on a stock car. I'd be more worried about the quality of the gas, stray away from older gas stations as they tend to have more sediments deposited in the bottom of their tanks that can get in your gas. The difference in brands is negligible.

The gains were made because of the oxygenated fuel, not because of the octane difference. Oxygenated fuels have a lower power stoichiometric and thus you have to run a richer AFR mixture then non oxygenated fuels to compensate. While oxygenated fuels will reduce gas mileage they are able to produce more energy during the combustion process.