It is posted as 87 OR higher as long as it's at least 87 there will be no damage to the engine.

 

My 03 Accord V6 6Speed Coupe ECM will adjust over time and deliver 10+ hp increase from 87 to 89.
It sounds like you know what you are talking about, where did you get the info on the Fit ECM?
If this is true, that the Fit ECM won't adjust, then this case is closed, period.
Thanks.

 

The fit allready has a somewhat high compression motor at 10.4:1... I remember my 1995 Mazda 626 with a 2.5l V6 asked for Premium even with it's low compression ratio of 9.2:1 (If i remember right...)... My neon also asked for 91 Octane at 9.6:1 (DOHC engine!)... there are several factors that mandate this... More ignition advance will usually mandate more octane... higher operating temperatures too as higher octane fuel has higher resistance to pre-ignition... improved breathing capacities through intakes, throttle bodies, headers, etc, will often give peak performance through using higher octane gas as the additional airflow in the engine will increase dynamic compression , and in the process, peak operating pressures...

The only times where you won't gain anything from using premium gas is if the car isn't equipped with a Knock Sensor (dunno for the Fit!)... in that case, it just won't give more timing advance and, as higher octane fuels burns more slowly, it will just end up burning in the exhaust, harming the catalyst on the long run... you also won't gain anything at higher altitudes as the barometric pressures are less then at sea levels, deacreasing your octane need in the process... your octane needs will also fall at lower ambient temperatures (as in the winter months!) as the lower intake air temperatures will increase knock resistance...

Personally, i use Premium in the hot summer months and Regular in our freaking cold quebec winter months!!

Marko!!

P.S. Contrary to some peoples beliefs, Premium fuel has a higher energy content but not by much... 1 or 2% at most!!

 

I've been running my Fit on the recommended 87 octane gas for four tanks now. Just recently, I switched over to 89 octane gas. I noticed a BIG difference in performance. I bet MPG will increase too. Even though the owner's manual only recommended 87 octane, that was referring to a stock Fit. Mine has a cold air intake on it right now, so I think I would need 89. I will never go back to 87 again! However, I believe that jumping up to 91 octane is overdoing it for me.

 

Interesting.

Do a blind test. Have someone fill up your tank so that you don't know which gas is in there.

You drive and record your impressions. Keep a log book.
Calculate mpg for that tank and the type of driving you do.

Repeat for several tankfuls then reveal the results.

There is no scientific proof that 89 octane is any better than 87 for your Fit.
You might change where you fill up with the 87. Top tier gas is a better choice for 87.

IF you have a car that requires 91 octane or better and you use gas that is less than 91 then you can expect lower mpg and performance. This is not the case for the Fit.

 

I was on a tank of 87 octane Chevron with Techron gas just before I refilled. Now, I'm running 89 octane Chevron with Techron gas. I wouldn't have noticed the difference in power if my Fit had a stock air box and if my CAI wasn't MR Technology-equipped.

 

87 Octane FTW!
Just use what is recommended in the Manual. Honda knows best
and if that wasnt enough to convince you...... ITS CHEAPER TOO!

 

Anybody tried to reset the car's PCM after putting premium fuel so that the PCM can learn it the right way?? I'm planning to try it and see if it helps as putting premium fuel did little when the car regularely ran on regular..!!

Marko!!

 

octane is nothing more than the resistance to knocking. knocking is the pre-detonation of fuel mixtures in the cylinder. the higher the rating the higher its resistance. it will not doing anything performance wise, you're psyching yourself out due to the fact u payed more for it you think it's doing anything.

 

octane is not "resistance to knocking". It's how easily it is ignited. Sorry, it just sounds weird saying octane is the resistance to knocking.
Higher octane=Harder to ignite.

 

+rep to this guy.
If your car was designed to run on 91, Honda would recommend it.
Higher octane is useless for us, unless your running boost applications or high temp situations where pre-ignition is more of an issue.

 

The octane rating is a measure of the resistance of gasoline and other fuels to detonation (engine knocking) in spark-ignition internal combustion engines. High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel. A lower-performance engine will not generally perform better with high-octane fuel, since the compression ratio is fixed by the engine design.

yes it is. learned it in autoshop this week. we had a 2 hour lecture and 1 hour video on just gasoline. kk thx

 

I have found that if I use anything less than premium grade (high octane) fuel, my fuel mileage drops 10%. .... The higher octane fuels are said to have cleansing additives, and don't create varnish buildup that is harmful to the fuel pump, filter, injectors, valves, seats, spark plugs, piston tops, skirts, catalytic converter, and 02 sensor. .... I also use an additive to prolong the storage life of the fuel due to the long periods that my car will sometimes sit without being driven. .... If I was to use the cheaper stuff, I would at sometime have to use a fuel system cleaner conditioner, and the savings would be nullified. .... With the limited performance enhancements that I've added, I also notice some improvement in performance.

 

Sorry, i've never heard it put that way. Resistance to detonation is much better
Or as your article states: "Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction"

 

Yes, I understand, and have taken courses and built numerous high performance automobile and racing motorcycle engines. 10.4:1 is what I would call a high compression ratio. With an in line tuning module that advances my timing and enriches the fuel mixture. A SRI, and 2 1/2" axle back pipe and iridium plugs, the little engine isn't quite a high performance engine, but I am getting descent acceleration and gas mileage. I have had to use premium fuel in air cooled VWs with only 8.5:1 comp. ratio, or detonation problems would pull the head studs out of the case. The 93 octane that is the highest where I live, is far from being high octane, and the owners manual list 87 as the absolute minimum to use. It is rediculous to think that a 16 valve 1.5 L. 4 cylinder that will rev to 6500 R.P.M.s and makes 109 H.P. isn't a high performance engine. My 1800 Goldwing only has 3 more H.P. and needs to be reprogramed to not overheat at low speeds, and I use the same fuel in it. The little motor in the Fit makes good power, the weight of the car it is in is what kills it. Mine is faster than stock, spins the tires like crazy in first, a little in second, and has power enough to pass cars on 2 lane highways. Mine does honestly run much better with higher octane fuel and the mileage diference offsets the price diference. I am sorry if this reply is goofy, but I need sleep.

 

Took some readings on my Datalogger... at 6300Rpm, with IAT at 50°f, my computer gives 17° of advance with regular 87 Octane fuel... i just resetted my PCM and will check out with premium if it gives more advance...

Apparently these PCM adjusts themselves to differents octanes around the world so maybe it will be positive...

we'll see...

Marko!!

 

Ok... here are the results... the test was done going uphill on a specific hill at WOT in ''Drive'' and in similar conditions... Meteo, temperature, wind, etc...

The car seems torquier but not so much... (It's still stock!) it looses less speed going uphill when not at WOT and it gains a little more at WOT!!


87 Octane... (Recorded 2 days ago on datalogger!)

3000Rpm
-IAT -> 52°f
-ECT -> 181°f
-TPS -> 100% (WOT)
-Timing -> 13°

3500Rpm
-IAT -> 52°f
-ECT -> 181°f
-TPS -> 100% (WOT)
-Timing -> 14°

4000Rpm
-IAT -> 53°f
-ECT -> 182°f
-TPS -> WOT
-Timing -> 14°

4500Rpm
-IAT ->53°f
-ECT -> 182°f
-TPS -> WOT
-Timing -> 15°

5000Rpm
-IAT -> 53°f
-ECT -> 182°f
-TPM -> WOT
-Timing -> 15°

5500Rpm
-IAT -> 54°f
-ECT -> 183°f
-TPM -> WOT
-Timing -> 16°

6000Rpm
-IAT -> 55°f
-ECT -> 183°f
-TPM -> WOT
-Timing -> 17°

6500Rpm
-IAT -> 55°f
-ECT -> 184°f
-TPM -> WOT
-Timing -> 17°


.....with 92 Octane fuel... (after resetting the PCM and running in various conditions for 100km with the good gas in... city, hwy, cruise, WOT, etc!)

3000Rpm
-IAT -> 57°f
-ECT -> 180°f
-TPM -> WOT
-Timing -> 15°

3500Rpm
-IAT -> 57°f
-ECT -> 180°f
-TPM -> WOT
-Timing -> 16°

4000Rpm
-IAT -> 57°f
-ECT -> 181°f
-TPM -> WOT
-Timing -> 16°

4500Rpm
-IAT -> 58°f
-ECT -> 181°f
-TPM -> WOT
-Timing -> 17°

5000Rpm
-IAT -> 58°f
-ECT -> 181°f
-TPM -> WOT
-Timing -> 18°

5500Rpm
-IAT -> 58°f
-ECT -> 181°f
-TPM -> WOT
-Timing -> 18°

6000Rpm
-IAT -> 58°f
-ECT -> 182°f
-TPM -> WOT
-Timing -> 19°

6500Rpm
-IAT -> 58°f
-ECT -> 182°f
-TPM -> WOT
-Timing -> 20°


I think that to make good use of premium fuels in a fit, you have to completely empty the tank of 87 octane, fill up with premium and then reset the PCM... It did worked for me as we can see...

Marko!!

 

 

Actually, i tried it with 2 ounces of Acetone (150 Octane) in a tankful of premium and gained 1 degree at higher revs... like 5500Rpm +... didn't felt a difference...

As for fuel economy, i'm going for a 600km ride so i'm gonna see if it made a difference to reset the PCM!!

Marko!!

 

I agree with you. I own a gas station here in NJ and Im UNBRANDED as they say here.I have always purchased Sunoco gasoline except for one time they brought me a load of HESS. I never had a problem with Sunoco but the HESS gas ran like crap in my customers cars.It IS all about the additives