Octane does make a difference!
 

Since the day I bought my Fit I've been filling up on 89 octane gasoline. I've been getting consistent 250 miles on a full tank with about 70% highway driving. :o I felt this was normal for a new car for the initial break in period.

After 2 months and 3000 miles I was still getting the same numbers with the same 89 octane gas. I was a bit disappointed as my V8 BMW was getting around the same numbers. I read a thread in DIY section of Fitfreak about gasoline octane and how the Fit's engine probably couldn't advance timings to take advantage of the higher octane gas. I decided to try this theory myself and fill up on 87 octane. My first fill up I got 320 miles.

From now on, I will only fill up on 87. Seems like the higher octane gas was actually hindering the engine more than it was helping.

it was bult for 87 oct,,,you may be on to something

less octane fuel technically has more energy in it, not surprised you got more miles considering the engine was built to take advantage of it. I believe higher octane fuels are primarly used to more precisly control detonation time in more sophisticated engine setups that run higher compression rates.

87 octane.
 

Yay for 87 octane for the Fit.

i was getting a consistent 250 miles per tank while doing all city driving and fillinig up on 91 octane.last tank i filled up on 89 octane and got 270 mpg.the draw back is see is that the engine isnt running quite as smoothly with the lower octane so im gonna switch back to 91

Agree w/above - Higher octane = no predetonation under high compression. Not an issue with the Fit as it doesn't have a high compression engine.....

I'm the first to agree that higher octane is a waste of $$ in the Fit. I also mentioned somewhere before that in theory, you could get lower MPGs because of the lower volatility of higher octane gas.

But I have to say I'm really surprised that the difference in MPGs has been that noticable for people. I would have thought that it would have been so little you couldn't tell a difference (maybe on the order of .1 mpg)

Are you guys sure the driving conditions, etc are the same when you're driving with 87 octane vs. a 91+? That's quite an eye opener for me if so......

Read!!!
 

Decide for yourselves. Premium Fuel - Do You Really Need High Octane Gasoline?

I'm not willing to pay 20 cents more per gallon for nothing.

Even IF higher octane gasoline improves performance, the Fit is still a phucking slow azz car.

Happy pumping!:cool:

yup, your right. It's a waste of money

Only the autotragics. My Fit moves around perfectly fine, I find it quick and peppy.

Yes, I totally agree with you. My Fit moves around perfectly fine, too. I too find it QUICK and PEPPY. However, I still find my Fit a phucking slow azz car.

Thousand and thousand apologies for talking down on the Fits, I take it back a thousand times on the psa part.:(

Peace.

The Fit loves 87 - I tried Supreme and it was obvious that it was not liking that gas. Drove that tank out ASAP and refilled with 87 - purred like brand new! For me - it is nice spending 16 dollars to fill it up on half a tank! They laugh at the gas station where I pre-pay because often I come back in for my refund! They said that never happens.

Cat :x

this is interesting, as I have found (by watching my ScangaugeII) that with Shell premium, the timing DOES get advanced, but not by much. While cruising with 87 octane, I can usually get the IGN (ignition timing advance) to read around 33 if I really try for it.

However, I can make it up to 36 or even 37 CONSISTENTLY with Shell premium. Not saying that this makes an appreciable difference in performance, it probably doesn't. I haven't noticed a major change in gas milage, either.

While on the highway and using the cruise RESUME function from 60mph to 70 (to maintain consistency) on a flat, level road, my timing went from 11 (regular) to 17 (premium). While this doesn't prove that premium provides a significant (or even measurable) performance change, it it does, however, show that the Fit CAN adjust for premium, or at least, mine can, to a minor extent, if I work at it.

note: by "working at it," I mean modulating the throttle and watching the IGN number on the same flat, level road.

New cars will adjust for different octane levels but we are still better off with the 87.

Sugarphreak is dead correct here (very nice to find someone else that knows the truth here). High octane gas does have less BTU per gallon then low octane...its advantage is that is burns in a slower, more controlled manner, allowing modern cars with dual knock sensors and the like to very precisely control ignition advance. Looks like the ignition and fuel system on the Fit is basic enough, that is not really needed...this was part of the major reason I choose the Fit (though, if I put that KraftWerks Supercharger on....gonna have to run high octane).

Here is another tidbit for you. Here in Colorado, our lowest octane fuel is 85, premium is 91. There is a reason for this, at high altitudes fuel is less volatile, so no need to have super high octane ratings. I have been putting 85 in my Fit, no problems, and getting damn good mileage (worst 33, all city with a/c on, best 41 with a mixture of highway and mountain driving...car is a manual).

Do the same test at full throttle if you could. I am curious how much the Timing gets advanced with Premium at full throttle.

It's obvious the car is meant for low octane with the mileage numbers however if at full throttle the ECU advances the timing enough the high octane might bring slightly better power. Might be worth it for a drag strip or SCCA course.

Higher octane is ment for high compression engines. More octane = slower burn and can with stand a higher compression. For example the K series in my RSX can not run on lower octane. Since lower octain with burn easer it can detonate as the piston is compressing the gas before the spark. In a low compression engine like out FIT there is no worry of early detonation. When you run a high octain in the FITs engine the fuel burns slower and is not complely burned before the gases are sent out though the exhaust. Basically you are wasting some of the unburnt gas. Higher octane will not improve the FIT performance. In reality it will make the FIT slightly slower trying to ignite the slower burning gases.

OK, tell me this people.... My fit knocks when i use 87 like crazy! If i use 87, put it in paddle mode and cruise in a high gear *low RPMS* and jam on the gas all i hear is a constant ping pop pop ping then it evens out after about 10 seconds... no thanks i dont give a crap if it "saves me" MPG or a few cents per gallon, i'll use 91.

Sounds to me like you're trying to run in too high of a gear. Does it knock in "D" mode (i.e. using a proper gear at all times for speed and load conditions)? IMOA "lugging" an engine is much more harmful than spinning one.

Yes, it does it in D as well at times, but when I use 91 i can put it in 5th at 35 and slam the gas and it's as smooth as butter *granted, it doesn't go anywhere...* but still you know what i mean. Is there something wrong with my engine or is that pretty normal?

The thing is built for 87 octane. So given that,,, are you buying your fuel form a reputable dealer or no-name?. If your getting good gas and still getting knocks with 87 then I'd say something is wrong. That 10 seconds of pinging is not doing the tops of your pistons any good, avoid it at all costs and see if you can get it fixed or maybe you will have to run the higher octane to avoid it. Are you at a very high altitude where you live?