Octane VS fuel milage

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Quote:
There was a year when a Honda suddenly had 20 more hp. All it took was a better knock sensor and feedback control to unlock.


Which make/model Honda was that ?
 
Originally Posted By: LT4 Vette
Quote:
There was a year when a Honda suddenly had 20 more hp. All it took was a better knock sensor and feedback control to unlock.


Which make/model Honda was that ?


A review of the 2003 V-6 Accord in USAToday mentioned an increase of hp and torque when using premium:

"The Accord V-6 ratings assume regular-grade fuel, and Honda will market it as a regular-fuel engine. But — pssst — it's good for another 10 hp and 10-plus lbs.-ft. on premium, acknowledges V-6 engineer Asaki."
 
Originally Posted By: Shannow
Unless the engine is undergoing knock retard.

Then Octane can make all the difference.


Definitely. My VQ40 has had some spark knock on 87 since its first tank of gas. I don't notice any on 89 octane and it gets a little better mileage too.

The funny part is what the manual says about it: "Now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is not a cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load".

Wonder how many seconds they consider a short time and how it could actually be good for gas mileage...?
 
My VW is VERY sensitive to octane. I usually BYO to 90-91 but things liven up a LOT on 93. 87 is out of the question.

With a $.40c difference between 87 and 93, it's a no brainer.

I'd need +10% to break even, or 2mpg. I think I have that.

93 to 89 would be a more appropriate comparo, at $.30c

The higher prices go the increment to get premium becomes less of a factor. $.40c on $2 gas is meaningful, on $4 or $5 gas it's less so.
 
It all depends on weather conditions, engine tuning, and engine state of tune.

During the heat wave, I can feel the power getting pulled by the knock sensor in almost all my cars. So, the few very hot weeks in the summer, I run super. I'll run mid for a couple weeks before and after the heatwave. And, I can use low grade for ~8 months out of the year. This has been on my Nissans, Toyotas, Mazdas, and Kia.

MPG and power drops like a rock when the knock sensor is aggressive. Its obvious. And, you have to be senseless not to notice it.
 
Dr -
I am a ZX2 expert.
You have 9.6 compression.
Unless you have mods, especially a better computer or chip or programming, you should not need anything but regular 87 in that car.
[UNLESS you have the rare S/R model! Then use mid grade or premium!]

One mod that is very popular is to unplug the knock sensor on that car. They are not very sophisticated and actuate for all sorts of noise and vibrations. This will smooth out your full power and net you a few HP.
 
Tune, tune, tune. When the recommended fuel for your vehicle is 87 octane, use it, cause the manufacturer TUNED it for that. Theres no real use of using a high octane than your car was tuned for. "butt dyno" means nothing and estimating your gas mileage is no accurate due to driving different places, conditions of the road, outside temp/humidity, these so many factors. For example, colder air coming into your engine will cause more horsepower to be produced than a hot day. Tune is everything. You could have your vehicle tuned for a higher octane, producing higher horsepower, if you keep the same driving style, you will get better gas mileage. As far as how much depends on your motor and the tune, is it worth it for a stock motor, probably not.
 
Originally Posted By: ARB1977
I tried it a few times in the Taco and did nothing. 87 is what I use along with FP60 plus.


Same here with my Ford 2.0 Zetec & 4.6 Modular. With LC 20 & FP60 I lessened the surging in my Zetec I had since new. My 4.6 developed a knock on any 87 octane fuel I used. After using LC20 & FP60 with 87 octane fuel my knock disappeared. I still have a light ping upon light throttle under load sometimes, though not all the times. Though this only happens when the temps are in the upper 50 degrees and below sometimes. I have no pinging in the warmer temps.

For me using the FP60 for my 87 octane fuel is less costly than using Hi-Test fuel. Hi-Test is $0.40 a gallon more. FP 60 is around $0.04 a gallon. Plus I get the benefit of extra fuel system cleaning.

Whimsey
 
Last edited:
Originally Posted By: Digital2k2
Originally Posted By: Shannow
Unless the engine is undergoing knock retard.

Then Octane can make all the difference.


Definitely. My VQ40 has had some spark knock on 87 since its first tank of gas. I don't notice any on 89 octane and it gets a little better mileage too.

The funny part is what the manual says about it: "Now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is not a cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load".

Wonder how many seconds they consider a short time and how it could actually be good for gas mileage...?


I'd be interested in hearing more about this. I have been running 87 in my 07 xterra since I got it, but I have been meaning to try 89 at least to see what the result is. I believe that Nissan jumped around a little on the octane recommendation for the 4.0 and the other VQ's recommend premium as well.
 
Originally Posted By: Coastal

I'd be interested in hearing more about this. I have been running 87 in my 07 xterra since I got it, but I have been meaning to try 89 at least to see what the result is. I believe that Nissan jumped around a little on the octane recommendation for the 4.0 and the other VQ's recommend premium as well.


They changed the wording for each year Frontier from 05 to 09. As far as I know 09+ has the same wording. When the VQ40DE first came out they recommended using premium fuel only.
Reading on the clubfrontier forums some have reported 1.5 to 2mpg better from using premium.
 
I've run 89 in my 10.0:1 Duratec 3.0(MZI) fuel economy went down.

I've also run 89 in my turbocharged Chrysler. Knocked like a [son of a gun].

I've have also run 89 in a Hyundai XG300. It actually felt a little more sluggish (it is a Buick Park Avenue size car being pulled around by Hyundai's 192hp version of the Mitsubishi 6G72)Fuel economy seemed unaffected as indicated by the in dash meter.

I've also run 89 in a 3.5 Diamante' that indicated that premium fuel was "recommended" No discernible difference in power or fuel economy. I probably could have just as easily run 87.

I haven't seen an improvement yet from 89. My tests all came back with negative or no improvement. But that doesn't mean you won't. Try a little.
 
Quote:
Reading on the clubfrontier forums some have reported 1.5 to 2mpg better from using premium.
Even if accurate, does that more than cover the added cost of the premium gasoline? Careful records and calculation of the total fuel cost per mile, not just miles per gallon, are needed.

By the way, there are only three reasons any modern engine pings--
--Some electronic component of the system is kaput. Fix it.
--Carbon has built up in the combustion chamber and is igniting the fuel charge before the spark fires. Use a combustion chamber cleaner.
--The engine was designed to make a light, harmless ping under heavy load. Live with it.
There is no good reason to buyer higher octane gas for a pinging engine.
 
Originally Posted By: Ken2
Quote:
Reading on the clubfrontier forums some have reported 1.5 to 2mpg better from using premium.
Even if accurate, does that more than cover the added cost of the premium gasoline? Careful records and calculation of the total fuel cost per mile, not just miles per gallon, are needed.

By the way, there are only three reasons any modern engine pings--
--Some electronic component of the system is kaput. Fix it.
--Carbon has built up in the combustion chamber and is igniting the fuel charge before the spark fires. Use a combustion chamber cleaner.
--The engine was designed to make a light, harmless ping under heavy load. Live with it.
There is no good reason to buyer higher octane gas for a pinging engine.




Premium cost`s .20 cents more per gallon. In my vehicle,that recommends premium to begin with, it`s a no brainer.
 
I saw an improvement in gas mileage (on long trips) with higher octane fuel in my 2001 GMC truck with 5.3L engine. There is a special feature in the computer that does an octane test when there is a change in the fuel tank level of more than (approx) 5 gallons. The ignition timing is advanced a little more when the engine cranks over and the amount of knock is detected. The computer will than calculate what octane it thinks it is using, and a new spark map will be used. I have not noticed an improvement around town. There is a place in Canada called Westers Tune that also discovered this feature and can reprogram your GM ECM to take full advantage of this feature.
 
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