i dunno then im not a expert, just trying to think logically. oh well i learn something new everyday

my dad has a '95 toyota camry v6 with 325,000 miles but he uses 91 octane all the time as it "requires premium unleaded fuel". i know this has nothing to do with anything, but damn 325k miles with no engine problems is pretty damn good.

so if i was anybody, going by the book isn't too bad neither.

 

States (or regions) that are at higher altitudes sell lower octane gas - just buy "regular" and you should be fine. Read the last 2 paragraphs of this article:
http://en.wikipedia.org/wiki/Octane_rating

 

The J30 in the Accord and previous gen Odyssey only requires regular unleaded.

The J32 in the TL requires premium.

 

87 is perfectly fine. the engine was designed for it...and with all the variable timing oxygen sensors and computers, their intended design is to work with the fuel so the engine can operate properly. buying higher octane fuel is a waste of money and does nothing for your engine(unless it's knocking or modified) as stated before. i just don't understand the rational behind buying something that doesn't help one's engine and then almost brag about it. i guess some people want to sound cool by claiming to buy high octane fuel when they sound silly.

why do they sound silly? well, the reason is based on physics. each engine or car may be different and stated HP numbers are usually just pub-points and bragging rights and cannot be proved one way or the other until one sits their car on a dyno(which vary greatly between pulls let alone compared to the guy's down the street. but there is one thing that is constant. and that is the fuel. 86 octane 87octane 89 octane 90 octane 91 octane 93 octane all have one thing in common......they all have the the exact same potential energy per gallon as the other! about 120,000 BTU's per gallon! so what does this mean? it means it is physically impossible for an engine to extract more power from 93 octane fuel over 87 octane. impossible!!!

just assume the 120,000BTU's as a constant. and the volumetric efficiency of the (unaltered)engine as another constant. the fit's engine's not going to care what fuel it has in it. now change the compression ration of the engine and you've increased the volumetric efficiency and required a higher octane fuel to prevent premature detonation, but you have NOT added more BTU's to the fuel, just altered how the engine processes the fuel which increases one's horsepower.

use what the engine's been designed....take the money you save and buy a turbo charger and then buy higher octane gas! so until you alter the engine or wear it out, don't waste your money!

 

your odyssey was designed to run different types of fuels, but the engine performs best with premium, but you can also run regular unleaded because the engine can compensate like retarding the timing with out any detonation. but the honda fit was designed to use 87 octane, if you put 93 octane in your car, you probably wont gain any power you may lose power bescause the engine might not burn all the fuel during the combustion( 93 octane takes longer to burn) it will advance your timing so you might lose power there.
finding out what octane to use isnt an exact science, if you install an intake and exhaust you might want to go up to the next octane level to see if you gain any extra power if not then just go back to regular

 

i'm not aware of 93 octane burning slower than 87, but i do know that it's tendency to pre-ignite due to pressure or hot-spots in the cylinder is lower than 87 octane.

as for the intake and exhaust, the engine has not technically been altered in the sense of needing higher octane fuel. the intake is only making the breathing in easier and the exhaust is optimising the path out of the engine. this can increase the engine's ability to use the fuel, it does not however alter how the fuel ignites, that is still done by the sparkplug(which we hope is the case). adding more oxygen would not have an effect to weather the fuel pre-ignites. it does give the engine a more dense oxygen charge, which, the oxygen sensor/computer would then adjust the fuel ratio at the injectors to allow more fuel into the cylinder giving you more power, but once again, not giving the fuel any more umpfff, just more fuel to the cylinder.

 

I usually don't trust a lot of the things I read on the internet unless it is from a credible source.

The issue over power is not the case or shouldn't be the case unless you are running a chip, forced induction, or swapped your engine for a small displacement motorcycle engine(the fit's engine is quite close).

You can feed your car milwaukee's best or miller genuine draft, but it all comes out the same color.

 

We have regular 87 and 89 with less than 10% ethanol added. The 89 costs less. Why would I use one over the other? I thought ethanol burns cleaner and doesn't leave as many deposits over time? All my previous cars required premium 91+ so that was a no brainer.

Also, the Fit's 1.5L is 10.4:1 CR. That's pretty high for such low octane. Any reason for that? Is there some new technology I'm not aware of?

 

While in New Jersey I noticed Sunoco Ultra-93 Gas was the same price as Regular Gas in New York City and I treated my Fit to some of it. "NEVER AGAIN" The Fit felt sluggish and MPG was down.

I have a Sport Automatic and while using the paddle shifters to shift down to 4 to Pass, was to no avail. Definitely (In my opinion) don't waste your money on higher octane gas. It took me 2 Regular Gas fill-ups to get my baby back to normal.

 

my integra vtec motor needs 91 octane, and has a compression ratio of 10.1:1, but it also redlines at 8200 rpms.
yet, the fit uses 87 octane but has a higher compression ratio.

i believe all the new technology they put into the L15a helps to make it less vulnerable to detonation/pinging than my b18c1 motor. i've read that the pistons have special coatings on them (same coating used in the integra Type R motor) to keep them running cooler and the motor itself is a new design that is suppose to be better than previous generation D-series motors.

if you stick to what the owner's manual says you should be fine. they've done their testing and such and found the best octane rating for the particular motor.

 

unless your fit is running a high compression which it's not then you're wasting your money.

 

OH NOES!!! AN EXTRA $3 A TANK!!!

i've got an intake on mine and i've been running on 91 ever since and i havent seen but a loss of about 1mpg from when i didn't have the intake...

just my $.02

 

FYI...the Fit's 1.5L is high compression (10.4:1). However it only requires 87 octane per Honda. Someone posted it has a special coating on the pistons. I have no idea about that. I tried 89 once because it's cheaper here. I'm sticking with 87 now.

 

just use what honda says, they made the motor

 

My mpg went down with 89oct. I filled up with 87 the next tank and Im back where I started from.

I also added an intake with the 89oct fill up. Mpg is in my sig. Lost 2-3mpg

 

i figure it cant hurt other than my wallet to put shell 93 in and thats what i have been doing.... never got 87.. dont some gas companies put more detergents in "premium"?

But onto the topic that honda recommends 87, manual says 87 or above... i also like to think in the way that since this is an "economy" car, lots of pressure to Honda that they cannot recommend you use premium gas since the press would be bashing the car, higher fuel cost compare to other cars in same class, etc..

 

Why is it that so many people who know the least, seem to know it the loudest?

There are a few things to take in to account when deciding whether or not to use higher octane fuel. Any car with a knock sensor can adapt to lower octane fuel. Many cars with a knock sensor can adapt to higher octane fuel.

If a given car has a knock sensor, and higher octane fuel, then the fuel injection computer can use that information to advance the engine timing and make the fuel mix leaner, yielding better power and/or better fuel economy.

To make the blanket statement that it makes no difference is foolish unless backed up with information about what's inside the F.I. program. If a car's computer is programmed with a different fuel/spark curve for better fuel, then that particular car can take advantage of higher octane fuel. If a car's computer is given any sort of adaptive programming, then it can learn to take advantage of better fuel. I don't claim to know what Honda put in, but I did want to correct a few people who are making statements that can't be verified.

 

Correct - that's why the manual recommends 87 OR HIGHER. Most modern vehicles have sensors that can adapt to different fuel types.

My mother's G35 achieves the best power with premium fuel. When regular fuel is used the car retards the timing and you can feel the power reduction, but it doesn't damage anything as detonation doesn't occur. But to her the power doesn't matter driving around the city. We use premium fuel when on long highway trips as it gets better fuel economy and better passing power.

My '85 BMW actually had less power running on 93 octane as it doesn't have the technology to advance the timing to adjust for the fuel. However, when I added a Dinan chip I had to use 93 as it would detonate on 87 because of the timing advancement introduced by the chip.

 

Yes the fits engine has a higher compression then some engines, BUT as some have said technology has helped them to run with a lower grade gas, I also think the feather weight of the fit has alot to do with it also. Look at motorcycles. Yes some need to run 93 but they turn 13-15k and make 135hp and up on 1,000cc's. But they are 420lbs or so and I think that has alot to do with it. I get a kick out of the fact my 996 ducati makes more power then my fit and the engine is smaller.

The fits needs 87, run 87. Unless you are boosting the motor or have internal motorwork done you are pissing money away.

before I sold my stg4 hybird wrx I was running 93 or 94 when I could find it....And I KNEW when I got shitty gas, car would knock like crazy and you could just feel the car stutter and slow down. I would sometimes splash in some race fuel when I got crappy fuel, but then again I was running 18 psi and had tons of mods. I had the first wrx with a sti 6spd tranny in jersey with a working dccd and I think I was one of the first on the eastern seaboard. Car was a beast but when I was done it needed 93 and if it didn't get good gas would run like crap.

moral of the story unless your car is silly fast and NEEDS the high test leave it be and run 87.

 

How do you know what the Fit needs? Do you speak from experience of your own experimentation with different fuel grades and resulting performance/mileage?

The Fit's own manual states "87 or higher". To me, that could be implying that it has the technology to take advantage of higher grade fuels. Or it could simply mean "use what's available as long as it's at least 87".

Perhaps it's better to examine the extent to which the car can take advantage of higher octane.

In terms of mileage, if you were able to acheive a 2mpg increase, it would simply not be cost-effective to use 93 octane. You really would be pissing your money away even though you see a slight mileage increase.

But what if it was combined with a performance increase? It then may be worth it to some people to use 93 octane fuel.

All the opinions here aren't worth jack. Hard data is where it's at. I plan to do my own experimentation with fuel grades, tire pressures, etc but I feel I need to wait until the engine has broken-in properly.