saving4one

Since moving back to NY from CA (where the highest octane one could get was 91), I'm wondering which would be better in the S, 93 or 91 with no ethanol?

Conedodger

That is a great question that I'd like the answer to. I've run 93 since mine was new because it is so widely available, plus my tune added a couple of years ago is based on 93. I'm finding 91 no ethanol is becoming easier to find recently and that is what I run in the kit car.

A 2

https://www.corvetteforum.com/forums...post1578137020

I use 91

saving4one

Thanks for that ^ A2. I will give it a try, I've been running 93/94 since my return to the east coast, mostly because of the lack of it in CA. There was an ethanol free 91 at a station in OR (about 60 miles from where I lived in CA) but it was a 50c premium.
I have a Sunoco right in my town with ethanol free 91, and it is no more expensive than the 93 across the street. I need to go back to that link and get the app for locating ethanol free stations.....

NNY S2k

Me too.
Levi

Chuck S

The age old "which is better" question omitting, as usual, the "for what?" part of the question. Fuel economy? Acceleration? Manufacturing and transport tolerances probably make 91 vs 93 PII (preoccupation with insignificant increments).

There are boatloads of tests view-able on line which show that within reason and in specific engines higher octane gasoline will produce more power than low octane. 87 vs 93 for example. Some numbers are insignificant, others are much higher. Different "tunes" for the engine are commonly needed to take any advantage. Within the realm of whatever ECU is bolted under the dash is really what I'm interested in.

My MY06 S2000 was tuned on Shell 93 and I run it nearly exclusively on Shell 93 for that reason alone. It admittedly feels no different on BrandX 93 or, from limited butt testing, with the 91 as available in some parts of the country as the ECU makes subtle changes in tune constantly. I do get noticeably more power when I run my 2017 Ford Expedition on 93 octane vs her normal diet of 87 and there are published data on just how much more power this fuel produces in the twin turbocharged 3.5 liter EcoBoost engine in the truck. I run 93 when towing but the truck has more than enough power on 87 to handle my 6000 pound camper. Supposedly the truck gets better fuel economy on 93 but I can't confirm and it would need to be very significant to offset the 25% - 30% premium cost for "premium" fuel.

Honda wants a minimum octane rating of 91.

-- Chuck

Crazy_Schizo

About 5 years ago, I had to replace all the rubber gaskets in my two year old lawnmower. The ethanol in the fuel had completely destroyed them. At that point, I completely switched over to ethanol-free fuel for all my gasoline engines.

I've been running 91 octane for the twelve years I've had my S2000, and ethanol-free fuel for the last five years, with no issues. Unless you have a custom ECU tune to utilize 93 octane, you should be fine on the 91. Ethanol-free is your choice, but after witnessing what it did to a small engine, I would not want to chance that happening to the S2000.