Premium gas gives 2-3 more horsepower in turbo models (confirmed by Honda rep)

jks said:

Honda's lead power train engineer, Yuji Matsumochi, doesn't agree that there is any power advantage to using premium. See the interview starting at min 5:

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Great info since I just picked up an EX-T

Maybe it's just me, but the engineer doesn't seem 100% sure of his answer. See about 3:28 where he says "Hmmm" and gives a slight "not sure, let me think about it" face.

Also using a higher octane than your car can use can actually decrease power (and dirty things up).

If it can't take advantage of higher octane, don't forget about ethanol free gas. www.pure-gas.org

Slickone said:

Maybe it's just me, but the engineer doesn't seem 100% sure of his answer. See about 3:28 where he says "Hmmm" and gives a slight "not sure, let me think about it" face.

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Have you worked with Japanese engineers with limited English proficiency? I have, for a decade, and definitely don't read that into this exchange.

dick w said:

Have you worked with Japanese engineers with limited English proficiency? I have, for a decade, and definitely don't read that into this exchange.

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He was speaking Japanese. And he's a human, which I am familiar with.

This is a silly post, the higher octane fuel has no more energy in it, in fact it has ever so slightly less. The higher octane fuel is a waste of your money unless detonation is an issue. In this vehicle it is not necessary.

Slickone said:

He was speaking Japanese. And he's a human, which I am familiar with.

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I'm pretty confident Matsumochi-san speaks enough English to have been translating in his head, and listening to the translation, at the same time. But think what you want.

Even if you don't gain hp, pulled timing can be really annoying. So although the ecu can prevent detonation, your power band will have "holes" where the car is pulling away potential power.

I had a turbo on my 1.5 liter Fit engine which is basically the same motor as the civic's and it pulled timing often on 91 octane.
It did make more power at 170 to the wheels and 170 torque but still. You have to consider that you're asking a lot from such a small engine. The more precise fuel control , the better.

DrivenSoul said:

Even if you don't gain hp, pulled timing can be really annoying. So although the ecu can prevent detonation, your power band will have "holes" where the car is pulling away potential power.

I had a turbo on my 1.5 liter Fit engine which is basically the same motor as the civic's and it pulled timing often on 91 octane.
It did make more power at 170 to the wheels and 170 torque but still. You have to consider that you're asking a lot from such a small engine. The more precise fuel control , the better.

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How did you know your Fit was pulling timing with 91 octane? Butt dyno?

To be fair, it's going to depend on ECU mapping. If the parameters allow it, more power can be gained by using higher octane fuel. Honda's engineers suggest no. But we won't know for sure until someone does a more scientific comparo (i.e. dyno).

Hyundai's 2.0T is a textbook example:
http://www.turbohkforums.com/t768-finally-hyundai-answers-me-directly-about-octane

civvie said:

How did you know your Fit was pulling timing with 91 octane? Butt dyno?

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Yes, I felt it while driving. But also when my car was getting dyno tuned during a spread for a performance car magazine, the tuner (who is the owner of Hondata) also experienced a lot of knocking - which I distinctly heard from under the hood.
At that point the tuner (Doug MacMillan) even suggested that I should try E85 and that the car would benefit an easy 30hp with the proper tune.

I agree with the above post. I think that some testing should definitely be done before confidently letting your poor boosted engine see 87 for the rest of it's life.

The only way to prove/disprove is with some datalogging. It will be difficult in the real world for an apples to apples comparison due to many factors (engine coolant temp, barometric pressure, intake manifold temp, switching out fuels and knowing you have 100% of the octane rated fuel in the lines, etc..). However, this argument is irrelevant until we start seeing data on spark timing set values (engine cal) and actual recorded values after the correction factors for temp and knock sensor.

Needless to say, someone's butt dyno is not a calibrated instrument, no matter how much he defends it on the Internet.

I'm not sure if you're referring to me, but if you are - we confirmed knock on 91 with the my turbocharged L15 engine by ear and from datalog on a Hondata Flashpro and it took quite a bit of tuning to correct it. Sorry I can't go into more detail but I'm no engineer, just a simpleton with a curiosity who wants the best for my engine.
You're right that right now it's irrelevant. But what we're both on the same page about at least is that it SHOULD be tested, not brushed under the rug and left for the engine to use 87 with no questions asked.

DrivenSoul said:

I'm not sure if you're referring to me,

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No, I'm speaking in generalities. Internet forums are full of mis-informed, single data point topics and wanted to just say to hold off on the debate until we have data

"In God we trust, all others must bring data" -Deming

mjones5 said:

HondaMan - do you know where Honda hid the second "easter egg" ? The trainer asked because he doesn't know but thinks it is somewhere in the infotainment system.

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in a little rubber mat in the center console. The underneath has a plane and a race car on it.

I feel like the whole point of 2 - 3 hp is moot as its not something you're ever going to feel and will fall in the realm of "margin for error". You're going to pay a lot more for 91 - 93 octane gas, with virtually no benefits and likely lower gas mileage.