Highest Octane For Stock ECU??

JoeD

Doubtful.

The only production-car I can think of which was optimized for anything but 91 is the Veyron. Everything else is made to run on 91-octane, as California is the biggest car-market in the country.

Mix any octane of fuel you want in a 370Z...there will be no varience on a dyno greater than what there would have been even if you didn't change the gas from pull-to-pull.

ZzzZz

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

rudi

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

Mercennarius

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.