Chopper

Read the E-zine article,it's right on the money.

67mustang302

Higher octane fuel can help. The higher octane pump gasoline(this is especially true for race fuels) is blended from better quality base stocks. The base stock fuels for premium is not the same stuff as the base stock fuels for lower octane(usually). The higher octane fuels usually have a slightly more refined base stock that is going to burn cleaner due to a reduced amount of impurities. The types of impurities that are in lower quality fuels can leave nasty deposits. As far as performance, you won't gain anything unless you can alter the engine to get higher cylinder pressure from using higher octane fuel without detonating. The engine will run cleaner and last longer on premium, but may not make any more power from it without modifications or high compression to begin with. Most street cars that are modest compression won't really see any benefit from higher octane fuels other than being better able to pass emissions past 100,000 miles, and will maintain better power from less deposit buildup after the engine has some miles on it.

bwkelley76

I'm gonna just jump right in here for good reason.

I think you guys will enjoy this.

Using a good higher octane fuel is a minimum of $100 cheaper per year at the pump and is way cheaper in the long-run when it comes to engine wear and tear/maintenance.

I'm an ASE Cert tech with 16 years experience and this is one of my specialties. I'm currently advancing in my career and adding a Clean-Air Car Course and California Smog license to the credentials.

I spoke in depth with my class and instructor recently about this very topic, and this thread is a great opportunity to share our findings with you all.

Al little theory for the weary ... (Chicken Soup for the Combustion Chamber) Read on and you'll get the joke...

Higher octane fuel allows your engine to run cooler internally, reduces Nox emissions, carbon buildup, and assists with the longevity of your combustion chamber, valve-train, and other components, and allows for better fuel mileage.

Why is it so much better on your engine and how does it yield better fuel economy?

Higher octane fuel is a better refined fuel formulation meaning it has Less JUNK in it (yes that means water in some cases). It burns cooler/slower and doesn't allow the combustion chamber to get too hot. Getting too hot over-burns (WASTES) fuel and causing detonation which can blow head gaskets, burn valves, and can eventually break pistons and rotating parts.

You can't always hear detonation either so don't think your engine isn't detonating to some degree when using crap fuel. When an engine detonates it consumes more fuel because the fuel vaporizes too soon making it less effective at the time it's needed for the power stroke. A computer controlled vehicle adds more fuel (more and more crappy stuff if you're using crap fuel) to compensate for this.

A little experiment for the mind here. If you take a gallon of gas and delude it with water and other impurities, a computer controlled vehicle will probably allow you to run it through an engine without too much trouble or obvious complaint. Guess what, it will consume it quickly though since it will turn the fuel control to full-blast to compensate for the delusion. You have no idea until you realize that holy crap your car isn't getting the mileage you expected, so what do you do? You look for the cheapest gas instead if giving the car what it really needs! You blame it on the car, not what you're feeding it!

So don't think you can fool your car's computer. It wants a certain amount of fuel (octane) and it will keep adding fuel until it gets what it wants.

Also do you want these impurities going through your engine instead of pure fuel? (most are too small for your filter to catch) What do you think happens to the junk after it burns? Ever looked at the bottom of grandma's gas oven? YUCK, that's what your EGR passages look like and I know this because I've had to clean them to allow a car to pass an emissions test.

Here's a more in-depth view on exactly why higher octane fuel will produce better fuel mileage on a computer controlled vehicle. (Usually .5-1 full MPG in most cases, and more in others)

The O2 sensor in a computer controlled vehicle controls the amount of fuel that is added from the injectors but IT READS OXYGEN ONLY. So in essence you could run a computer controlled car on chicken soup (although it probably wouldn't burn too well) and the O2 sensor wouldn't care. If the soup did it's job and actually burned and made exhaust gasses then the O2 sensor would add or subtract the amount of soup it needed to obtain the correct amount of oxygen as a byproduct. All it cares about is oxygen.

As we said earlier higher octane fuel burns slower. This as well as it's purity/density causes less oxygen to be released into the exhaust stream. Lower octane fuel burns too hot and sometimes leaves too much oxygen in the mix. The crappy gas is telling the O2 sensor to add more fuel and the system keeps doing so until it reaches the proper mixture. So it's basically going to use more fuel to achieve what the Higher octane fuel achieves easily.

With the latest technology (OBD-2 from 1996 to current) just about any vehicle can run on 87 octane or maybe even less. Efficiently? NO. Long-term is it the best thing for your vehicle? NO

Personally I run Chevron 91 octane with Techron in vehicles I care about.

Here's the math proving what you save using higher octane fuel (this does not calculate the maintenance and wear and tear on your engine from crap gas either)

-The average person drives a vehicle let's say 20k miles per year.

-Average fuel mileage is let's say 20MPG.

-That's 1000 gallons of gas per year your vehicle consumes.

-At $4 per gallon that's $4,000 you spend on 87 octane.

With the above figures let's say you used 91 octane fuel and got an average of 21 MPG, a 1 MPG gain, therefore only consuming 950 gallons (952.xxxx actual)

-At $4.10 (ten cents more) per gallon for 950 gallons you spend $3, 895.00, saving you a minimum of $100.00 in a year

It's up to you. I ran my '90 LX Mustang on 91 octane Chevron and never got less than 19MPG with a combo of highway and freeway.

Don't blame your car (or your kids) for being "fat" if you feed them junk!

maxshuty

I see a debate coming on here!

GreyStang

Nice post bwkelley & well worded. This octane issue comes up quite a bit here & probably at every other car forum too. There is a lot of misinformation & just plain ignorance on the topic of octane. I'm no science major student myself lol, but read your post objectively & agree you have some valid points. Because I have no scientific tech background myself, I let google do some my work for me

What do you think of this:

http://www.projectsamurai.com/tech/octane.html

Yes the reactions a car has to different gas octanes can differ because the onboard computers often self-adjust to take advantage of better quality fuel, but when & where do you know to draw the line? Should I go to the airport & fill my car up with aviation fuel? (I believe is around 140 octane)

I have heard that running too high of octane can eventually cause problems to an engine because of deposit accumulation.. Maybe only in extreme situations but, any truth to that?

05_mustang

Good post bwkelley.
I did this on my own & figured out that premium gas saved me money.
It costs more per tank full, but I go further on a tank.
I figured out I was saving .02 per mile using premium.
Trying to find premium without ethanol is the problem around here, I have found only 2 stations here so for that have it.

92stangerang

in all of the cars ive had i ran 93, mainly cause my dad is also ASE. ive never had a prob.

DeltaElite121

I only run 93 in all my cars. I can definitely feel a huge difference between fuel, and I last a little over half a week longer driving the way I do with premium (so about two weeks and 5 days before I need to fill.)

My dad tells me to buy the octane booster because he believes it works great with crap gas, and I just laugh at him. He's been trying to get me to do that FOREVER. He tells me it saves money, but really I don't save anything because the octane booster (which sucks ***, mind you) will end up costing me the same, if not more than premium gas.

So, I'm right there with you on this one.

bwkelley76

Thanks for the props guys, just trying to help. I speak from experience and it makes sense. As far as running too much octane you can do that also, especially in the higher RPM range as it would burn too slow. 2-Stroke engines on OHV's have a problem with this and it's tricky because they NEED the octane to keep things cool. Those engines fire twice as often as a 4-stroke so you can see the dilemma.

Keep in mind your O2 sensor can only adjust up to 10% as an average. Everything has a curve and the goal is to be in the middle, not exceeding the limits of your system either way. The cars that can adjust for octane are interesting (some production Fords were common for this in the late '90's. I would assume those have better parameters for timing and detonate less.

Jfsram

Even if there were differences in performance or mileage. I'd doubt any of you could feel it. The differences would be minor and would need sophisticated equipment to measure.

I mark down the miles or kilometers and amount of fuel to fill up EACH tank in all my cars.
A few of them I even tried to compare tank after tank, the difference between 87 and 93.

You need to do your own tests and see the difference. Most of my cars and past cars made no difference except 2. A 95 Ram and a turbo Shadow. Both of these had more kilometers / tank with higher octane but the difference was so small. It did not justify buying the more expensive fuel.

Another test I've done was with out daily driver/family car. I was especially curious of the results since this car has a premium fuel recommended on the gas door.
Guess what. After many tanks, of 91 vs 87. No difference in economy. Also tried a drag strip comparo. Drove to the track with the gas needle on E. Ran it on 87. Poured in 1 gallon of 94. My best numbers were with 87 octane.