91 vs. 93 octane in stock R

baldheadracing · Apr 18, 2019

remc86007 said:
While I'd like someone else to try 87 just to tell us what happens...I would strongly recommend against it.

I occasionally run 87E10 in the winter. On snow/cold I'm always light on the throttle, shifting below 2k rpm, and always below 0psi on the boost display. As the snow melts (I still have snow in my yard ffs), I'll use 91. In the summer I use 93E0. (93E0 is PITA to get - very few stations carry it around here.)

In my limited experience, 93E0 was faster than 94E10 or 91E0/E10 in terms of end-of-straight speed. However, it isn't like I did back-to-back testing, just tank-to-tank last summer, so weather, driver, etc., introduce a lot of variability. YMMV.

FifStreet · Apr 18, 2019

remc86007 said:
While I'd like someone else to try 87 just to tell us what happens...I would strongly recommend against it.

I've done it once. Nothing happens. The vehicles computer would recognize pre-ignition and reduce timing to prevent damage. But I wouldn't recommend doing it all the time.

Around me for some reason 91 is hard to find. 87, 89, 90, 93 are the more common choices. I will sometimes fill up with 93 and then when I get down to half a tank fill the rest with 87. its a pain. or if i'm lazy just fill it with mid grade 89 or 90. I've run just about every octane choice and ethanol mix (from 0% to 20%) and any change is barely perceivable to me in regular driving.

SixxSpeed · Apr 18, 2019

Up here in Canada, I believe the gas door says premium fuel is "recommended", meaning that you could get away with regular fuel if necessary- but I wouldn't rely on regular fuel religiously- only in a pinch would I use it.

Also, so long as you aren't putting your engine under heavy load- WOT pulls, etc, you should be more than fine. It's generally under heavy loads would you see maybe some knock and heavy engine timing retarding. While knock is a bad thing, again, in such a limited circumstance I think you'll be more than fine. Odds are you wouldn't even know its knocking.

jcp227 · Apr 18, 2019

I'm going to throw my two cents into this ring for what it is worth. Like someone said in a previous post, premimum is 98 octane over in Europe. If we brought our cars over there and ran there fuel our engines should remap and our motors should put out the 315 horsepower. I have been thinking about buying some Sunoco Race fuel and seeing if I notice a difference. If I decide on doing this I plan on filling my car about 5/8 to 3/4 full with 93 octane and then mix the rest with the race fuel. Anything over 98 octane will not benefit the car in anyway.

Type R 761 · Apr 18, 2019

jcp227 said:
I'm going to throw my two cents into this ring for what it is worth. Like someone said in a previous post, premimum is 98 octane over in Europe. If we brought our cars over there and ran there fuel our engines should remap and our motors should put out the 315 horsepower. I have been thinking about buying some Sunoco Race fuel and seeing if I notice a difference. If I decide on doing this I plan on filling my car about 5/8 to 3/4 full with 93 octane and then mix the rest with the race fuel. Anything over 98 octane will not benefit the car in anyway.

The video Honda pro Jason did in the UK with the Honda tech person stated that the car will advance timing up 99 Ron after that no benefit. And that NA/EU cars had same engine + factory tune. Also, 99 Ron is not equal to 99 octane in North America. Google it you will understand it better than I can explain. Up in Canada I can easily get Petro Canada 94 octane which is actually = to 101 RON according to their website because it contains 10 ethanol blend. Since it's only 2 to 4 cents more compared to their 91 octane that is = to 96-97RON. I fill up with 94 every time I fill to get the full 320hp or more since they underrated that engine....1 to 2$ per fill for extra performance on stock engine is cheap performance if you ask me.

jcp227 · Apr 19, 2019

Type R 761 said:
The video Honda pro Jason did in the UK with the Honda tech person stated that the car will advance timing up 99 Ron after that no benefit. And that NA/EU cars had same engine + factory tune. Also, 99 Ron is not equal to 99 octane in North America. Google it you will understand it better than I can explain. Up in Canada I can easily get Petro Canada 94 octane which is actually = to 101 RON according to their website because it contains 10 ethanol blend. Since it's only 2 to 4 cents more compared to their 91 octane that is = to 96-97RON. I fill up with 94 every time I fill to get the full 320hp or more since they underrated that engine....1 to 2$ per fill for extra performance on stock engine is cheap performance if you ask me.

Yes you are correct! Thank you for the correction.

The ratio of the two pressures provides the RON of the fuel in question. ... America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States.

CTtypeR · Apr 19, 2019

jcp227 said:
I'm going to throw my two cents into this ring for what it is worth. Like someone said in a previous post, premimum is 98 octane over in Europe. If we brought our cars over there and ran there fuel our engines should remap and our motors should put out the 315 horsepower. I have been thinking about buying some Sunoco Race fuel and seeing if I notice a difference. If I decide on doing this I plan on filling my car about 5/8 to 3/4 full with 93 octane and then mix the rest with the race fuel. Anything over 98 octane will not benefit the car in anyway.

You're not going to see any benefits from race fuel. It will be a net negative unless you tune for it

DKL · Apr 19, 2019

The only reason I'd consider 91 over 93 is I can get it without ethanol. I know the fuel system is designed for E10, but the car isn't driven much, and not at all in the winter.

EFEM1FB6FK8 · Apr 19, 2019

I guess I am crazy mixing 5 gallons of 100 octane to my tank every so often. Gas is going up like crazy in SoCal but thank god that 100 octane stays at $9.26 a gallon constantly.

Honda Civic 10th gen 91 vs. 93 octane in stock R 20190310_080341

Driveitlikeuboughtit · Apr 19, 2019

Is that race fuel unleaded?

CTtypeR · Apr 20, 2019

EFEM1FB6FK8 said:
I guess I am crazy mixing 5 gallons of 100 octane to my tank every so often. Gas is going up like crazy in SoCal but thank god that 100 octane stays at $9.26 a gallon constantly.

You're literally burning away money by doing that.

FLOPPER · Apr 20, 2019

CTtypeR said:
You're literally burning away money by doing that.

Great reason to get a tuning solution then.

Groundcontrol · Apr 22, 2019

MutatedMango said:
That's awesome that we have that tech now, also had no idea octane booster was a thing. How much does that cost and how exactly does it work?

I bought whatever brand the gas station I didn't really have much of a choice. I wouldn't make a habit of using it.

It was something like this:
https://www.walmart.com/ip/STP-Octa...MIzYzN-pDk4QIVhrfsCh3u1QA8EAQYAiABEgJTavD_BwE

spacemanspiff · Apr 22, 2019

Here's some information I found about octane ratings in Europe vs US.

Also, if you're in North America and you want to know more about which gas stations offer the highest quality fuel, the Top Tier Gas program is worth checking out as well.

BriteBlue · Apr 22, 2019

By me premium is 93 octane, there is no 91 octane, I understand some states only have 91 octane premium, at least that is what's typically available. I could mix 93 with 89 to get 91 but not sure it's worth the effort.

91 vs. 93 octane in stock R

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