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Up here in Ontario, Canada, there are still a few stations where the 91 octane is Ethanol-Free, mainly Costco and Canadian Tire and Shell. I do notice a marginally better mileage when using ethanol free gas and there's a Canadian Tire right by my house that I frequent for that reason. I tend to avoid Petro-Canada and Esso as I find less gas mileage the few times, I've used them and mainly they don't offer the same points as I get with CT (7c/L, which is definitely welcome when gas here is $2.20/L for 91 now) This list used to be more up to date but I still reference Pure Gas Ethanol-free gas stations in the U.S. and Canada from time to time if I'm in a new area
 

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I drive me 22 Si 550 (885 KM) miles a week, as my daily driver and have only used 87 Octane, with 10% Ethanol from Murphy's Gas, in a Walmart parking lot. 9,800 (15772 KM) miles on the clock and I have had zero issues. 91 is recommended, but I drive too much to feed it the good stuff, so it gets the 87.
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I drive me 22 Si 550 (885 KM) miles a week, as my daily driver and have only used 87 Octane, with 10% Ethanol from Murphy's Gas, in a Walmart parking lot. 9,800 (15772 KM) miles on the clock and I have had zero issues. 91 is recommended, but I drive too much to feed it the good stuff, so it gets the 87.
I'm in the same boat and same camp as you. I run 89 octane and I drive 700 kms a week on average, it runs perfectly fine. I have not seen any difference with respect to fuel economy and ignition timing between 89 octane and 91 octane, during my testing.

You have to keep in mind that Honda has a fixed declining ignition timing curve built into the ecu programming to account for owners who might run 87 octane. It reduces ignition timing under WOT throughout the rpm band to protect the engine, adding 91 octane won't allow the ecu to increase ignition timing beyond the mandatory timing reduction programming. The reason ecu tuners are gaining so much power is that they are removing the ignition timing reduction programming, and tuning timing specifically for 91-93 octane. I never thought of running 87 octane but it likely is perfectly safe, I just thought 89 was a nice medium point and still saves me some coin. Most of my miles are highway driving with zero boost, so I definitely don't benefit anything by running 91 octane, it just costs more.
 

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I'm in the same boat with the highway miles. I set the cruise at 81 MPH (130 KM) for over 40 minutes, so zero boost. I have a stretch of two-lane back roads with the cruise set at 70 MPH (113 KM), with an occasional spirited pass, but not everyday. If I didn't have such a long commute I would think about upping the octane, to see if there is a difference worth the extra coin, but like you said "I definitely don't benefit anything by running 91 octane, it just costs more." I like your input on the ECU. Personally, I like to think, that by never changing octanes, I have my ECU trained.
 

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I'm in the same boat with the highway miles. I set the cruise at 81 MPH (130 KM) for over 40 minutes, so zero boost. I have a stretch of two-lane back roads with the cruise set at 70 MPH (113 KM), with an occasional spirited pass, but not everyday. If I didn't have such a long commute I would think about upping the octane, to see if there is a difference worth the extra coin, but like you said "I definitely don't benefit anything by running 91 octane, it just costs more." I like your input on the ECU. Personally, I like to think, that by never changing octanes, I have my ECU trained.
Yeah a lot of people seemed to get overheated by the suggestion of running less than 91 but it all depends on your driving use, you and I would never see benefit from 91 IMO under our driving conditions.

When I first got the car I did some data logging with my scanner to see if ignition timing changed between 91 octane and 89 octane, and I could not detect any difference in timing. Then I read about the fixed timing reduction program in the factory ecu and it all made sense. When I changed from 91 octane to 89 octane I got a very slight increase in fuel economy, I can't say going down in octane increases fuel economy but I can say that it was not detrimental to fuel economy. These engines are pretty resistant to knock so I don't see the ecu reducing ignition timing further than it is programmed to do , I think we are good.
 

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I'm averaging 37.8 MPG (16.07 KPL), so 5 MPG better than my 2014 Accord Sport, Manual. I do miss the 18 gallon (68 L) tank on the Accord, and it's massive range. I stop for fuel every 3 days, currently with the Si. It says I'm out of fuel, but only takes 9.7 gallons (36.7 L) on average to refill. I know the tank is over 12 gallons (45 L), so Honda built in a lot of wiggle room after hitting 0 miles remaining.
 
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