Fuel and oil are hotly debated in all automotive forums. Conclusions are drawn by the debaters, most everyone else really isn't paying attention. Through the debate creditable info comes forth, but the debate goes on. I've gleaned enough insight into the ECU that controls my FIT to draw my own conclusions. Without the fuel of debate [which really should become more of a discussion] I would not have been lead to the conclusions I've drawn - nor would I really be part of the discussion, but that is what an open forum is all about.

I'm not surprised by the Yaris thread, but interested in seeing it. My daughter has asked if premium might benefit her's. I'm not that familiar with the Yaris ECU, but I've advised her not to waste her money. Thanks Woo for turning it up.

 

Our other car is a 2000 Honda Odyssey. The owner's manual states that this vehicle puts out 205 hp when using 87 octane. If 91 octane is used, the hp rating is increased to 210 hp.

Here is a quote from Edmund's:
"The second-generation Honda Odyssey is only a year old, and already it is recognized as the new minivan benchmark. It's powered by a 3.5-liter 24-valve VTEC V6 that produces up to 210 horsepower and 229 pound-feet of torque, according to Honda. To get that kind of power requires 91-octane, but with 87-octane fuel, the engine makes 205 horses and 217 lb-ft of torque. The V6 is based on the Accord's 3.0-liter engine but it offers more power, since the Odyssey's got a bit of extra girth."

Here is a link to that quote:
2000 Honda Odyssey

 

Interesting. Do you have that info from Honda? Or just Edmunds?

Also interesting that they DO say that for that car, but not for the Fit. Of course it's a decade later, they may have reasons for not saying it, even if it applies.

 

Bumping from 87 to a mere 91 yields a 12lb-ft gain at the crank for that decade old ~9.5:1 compression ratio 3.0L V6 (J30A) in case any of you rocket surgeons missed it. I would put money down that 93 would make nearly another 5lb-ft. There would likely be more to gain with higher compression.

These sorts of gains are not universally linear but in many cases they can be, sometimes they have a greater 2nd derivative sometimes they don't. These things are not black and white.

By the way that is just the gains at peak torque (VEmax) and says nothing of the real gains under the curve from the timing advance and leaning out.

 

I guess I misunderstood the request. I didn't know this was directed solely to the Honda Fit. I thought Steve244 was asking for ANY published material which states that higher octane does increase performance.
As for the info from Honda, I'll have to look for the Owner's Manual when I get back home from Idaho. It's been over 11 years now, but I recall reading that the higher octane fuel was recommended if the Odyssey was to be used for towing. I remember asking the salespeople about it's towing capacity.
As for using 91 octane, I performed a "simple" test last year. In doing so, I found that it did give "me" smoother acceleration off the line. I also found that the higher octane did return a bit more mpg. For the record, the small increase in mileage did not offset the increased fuel cost. I have since reverted to using 87 octane. If you are interested in reading the whole story, you can find my thread here:
91 Octane vs 87 Octane, which is better?

 

If we had the Honda manual stating only "87 or above" instead of "recommending 91" perhaps with the qualifier "when towing more than 3,500LBS" you might be on to something. However the Car and Driver dyno tests with that era Honda V6 render it moot. It actually lost power, both on the dyno and drag strip using premium.

Here are some other links that might be fuel for discussion:

I'm arsed if I can find anything better, and I thought I was a google-ninja. Apparently my google-fu is weak. DSM you're our only hope.

 

I'll bite.

Among others, the Genesis with the 4.6 Tau V8 makes 368HP/324Tq on 87 and 375/333 on 91 as well.

I don't really care what a magazine has to say about the matter. I don't go to random auto mags for technical information and then hold them up as gospel.

 

Why are you giving this as an example? Hyundai recommends premium in this.

 

Again with your cognitive dissonance.

What I posted is from the manual. Where in fact they specify regular, at least on the 2009 that I test drove a couple years ago.

If you want to use premium, which is 91 in much of the country and 93 here in Chicago, you get a bump in power which was also outlined.

In any event what sort of mental gymnastics does someone like yourself have to go through to try and get around the fact that the engine in question, the Tau 4.6 is 10.4:1 compression, just like our L15A's, yet you are completely glossing that over to make the claim that they recommend premium like that somehow negates what I was saying?

This is a perfect example for us. An OBD2 NA at 10.4:1CR makes more power and torque on premium vs regular. Fancy that.

Either way, you are acknowledging that they recommend premium in a 10.4:1CR. The reason we can get away with 87 is because of the knock sensor, which you can bet is pretty active as I find out everytime I have to use a tank of 87 out in the boonies.

Try using wikipedia as a source in your dissertation and see how it goes for you.

 

Where a manufacturer doesn't recommend or require premium, the power/efficiency advantage is negligible.

 

Hahahahaha

That is unadulterated bullshit. You just completely made that up. How would you even know that? You are not a calibrator, you have admitted you've never even tuned a car or used premium.

You are astoundingly obtuse and a compulsive liar.

I have a scantool and engine management in my car to monitor what it's doing and this is unequivocally one of the dumbest damn statements you have yet made. Which is a pretty tall order.

Back to ignore for you. Everyone else should do the same.

 

My first response wasn't very clear.

I'm hoping someone can find a published report showing performance gains using premium fuel where the manufacturer does not recommend or require using premium.

I don't dispute that where recommended/required, premium has an advantage. I'm not that obtuse. I have such a car and it only gets premium. The Fit isn't it.

I also don't dispute that the Fit advances timing more when it can, using premium. Just that this advance has a negligible effect on performance.

I appreciate your input. Besides the Odyssey, the Honda Pilot is another vehicle that has performance gains while using premium; it's recommended by Honda when towing over some weight.

 

Spark angle is directly tied to torque production you tard.

Horsepower is derived from torque.

All OBD2 vehicles can advance timing and lean out on better fuel.

The Fit has the capability to run as much as 50* of spark advance. QED. I have seen as much as 28* on 93 with 7 range plugs in favorable weather at WOT.

 

I see a strong correlation between octane and name-calling.

 

WALK AWAY, WALK AWAY DSM. Same goes to you Steve, we get it, you're stubborn and I guess you think you have some powers of suggestion to sway others to your side, which is really bordering on complete lunacy. For somebody that seems to believe everything that he reads, what is your problem with accepting that people who have hooked up actual scan guages and have seen the engine respond differently to a higher octane fuel? Are you calling all these people liars or what? Nobody has told you that you MUST buy higher octane. So why can't you just walk away? Some people who have the ability to comprehend what they read, may just decide to try a few tanks of premium, let them decide for themselves if it is beneficial for them. Why do you feel you must control other's wallets and protect them from having the ability to choose? If your owner's manual said at 150,000 miles you must drive off a bridge, would you do it? I mean it would be right there in black and white so it must be the end all be all. See how ignorant your stance is?

 

I'm thinking this new ranking system has really opened the door on 'thread ended points'. It's like staying on the merry-go-round to grab the gold ring.

These threads will never die anymore.......

 

Amen to that!

 

I agree. It's amazing how much of an e-fight some people try to make this issue out to be. Really? ... Seriously?

I, for one, have been incredibly skeptical about the argument that higher octane is noticeably beneficial to the L15 in the GE. My personal and professional experience has led me to believe that on an entirely stock set-up, if there were real benefits to using a higher octane, Honda wouldn't be so tight-lipped about it.

Regardless, I thought I'd give it a try. I had my strong doubts, but seeing as the worst that could happen is I'd have a couple less bucks for some cheeseburgers, it was worth testing out for myself. I've been keeping track of my mileage with 87 for awhile to get a pretty solid average, and this past tank I filled up with 91 (premium in CA).

My initial impression is that the engine does feel slightly more smooth. I wouldn't say it accelerates better or even call it more peppy, but it does seem that engine is less stressed about being wound up. That could be the increased or octane... or it could be a number of other factors. As it stands now, even with paying attention to every detail that my butt-dyno can, I wouldn't call the car quicker or more powerful. If I had blindly put in 91, and no one told me otherwise, I'd assume everything was normal.

I'm about half-way through this first tank of premium, so I can't really make any calls on mileage differences. My commute has been fairly consistent, the weather has been typically consistent (always sunny in SoCal), and with the needle at half-tank I've driven about as many miles as I usually do on 87.

Even if this tank proves the same average I'm used to, I still plan on filling up the next 3 tanks with premium. I'll withhold final judgement until I get a broader average. At least that way when I get called names in an octane debate, I'll be comfortable with the fact that I'm not the one being ignorant.

 

OP: too many variables are in play to call this. of course going to premium did not make your mpg go up. intake air temperature is the biggest factor in fuel economy

 

I've offered before to pay for half the cost of dyno tests comparing 87 with 91 octane on a stock fit. Offer still stands.

No I won't do my own. It's an automatic (dyno results are more reliable with a manual). Besides I'd feel silly.

If you're in the Atlanta area and want to play, here's a dyno shop in Marietta that has a $50, 3pull special on Thursday nights.

Needless to say it'll require two visits.

I'll buy the beer.