Ok I'll try to explain some of the things brought up.
Firstly, as Mark put it, gas is basically gas. If a gas is labeled as 87 octane, it is more or less, 87 octane. Something that does come up is variation from tank to tank. One day the gas might be 88 octane, another day it might be 86 octane but on average it's 87. This is why is possible to experience knock with one tank of gas but not another. What varies heavily between companies is the additives. This is not a major issue however as the additives make up a small part of the total volumn and are really more of a sales pitch than anything else.
Now then, as for ethanol blended gas, it does decrease gas mileage, this is a fact. From what I remember this is because the car has to inject slightly more gas to maintain the same AF ratio compared to non-blended gas. The power should be exactly the same using ethanol blended gas. Ethanol is used because it's a quick and easy way to increase the octane of gas, the only high octane gas around here is 94 octane blended fuel.

 

380 miles eh? Wow thats better than mine fore sure. Although I am not always just feathering the throttle...

For the most part I am feathering the throttle on the highway (50% of my driving at least)

I have been using chevron 94 and seen improvements on fuel mileage versus 87. Its a very small amount and it would probably be worth it just to put 87 in and save the money cause the miles just dont add up :P

The octane addiative myths and facts have been a very grey area. There are the hard facts, yes. But I searched google and couldn't find anything about 94 harming your engine. The spark plugs do their job and if the o2 sensors sense not enough o2, they either lean out the mixture or advance timing.

Just something to chew on

 

Is there any evidence that the computer will advance the timing to make up for the higher octane fuel? the AF ratio should stay the same regardless of what fuel you use, all that changes is the speed at which the fuel burns. Very few cars are setup to take advantage of higher octane fuels than they were designed for, meaning that if you put 94 octane fuel into a car designed for 87, it has no idea that you did that and just uses the same map it would use if you put 87 in. If the car was designed for 91 however and you put 87 in, the car would detect knock and retard the timing.
http://autorepair.about.com/od/gener.../aa060504a.htm
http://dnr.louisiana.gov/sec/execdiv.../trans/b/b.htm

 

My end-all source on gas quality explained...

http://vettenet.org/octane.html

Good read, I have posted it a few times here...

 

cool thanks

 

It also depends where you live. Some places (California for instance) have such strict gas regulations that the difference between brands is less than in other areas.

Or, due to the regulations, the gas in one area from one brand will be different from the gas from the same brand in another area. Thus even if there is a "better gas" it can be a localized phenomena that does not translate to other areas.

Also, having done some research on anti-trust law back in school, there have been several suits against various brands due to contracts they have in which they agree to sell to competitor brands for the same price they sell to their own stations. It is supposed to only be used if there is a shortage of one brand, so that the stations do not get screwed and have to raise their prices or face shortages. It is to protect the working man who runs his own station. Riiight.

Anyways, it turned out that in towns where the cost of transporting in fuel (in the mountains, remote locations, etc.) sending a truck for each individual brand was not cost effective. Thus, they will send in one truck loaded with Brand X, and it will top off the brand X, Y, Z stations in the town. It would not be worth the cost to send in a truck for each station. Sometimes they may switch it off so each gets a bit of the pie, but sometimes it is just always the same brand in all the stations.

The result is that the gas at all the stations is the same, it is all brand X, but they still advertise it as whatever brand is listed on the pump. This would appear to violate various provisions of the anti-trust laws, especially the "price-fixing" parts, but the courts have not been favorable to that argument so the practice continues.

Now, it has been a few years so I may be a little fuzzy on the details, but I am pretty sure that is the basics of how it works.

Just thought I would put that out there and let you all make your own conclusions.


edit: btw this is not conspiracy garbage, it is how the economics work out and can be verified if you want to spend the time poking around the various free legal research websites or have access to legal textbooks dealing with anti-trust.

 

That's actually a great question, someone should data log and dyno a car with 87, 91, 93 to see.

 

I have no evidence that timing will change. I know it will for pinging, so why not to better burn the fuel. I read that its a myth of 94 being a slower burning fuel. 94 only has a resistance to pinging, not to being ignited by a 35000V+ spark

"The flame speed of the conventionally ignited mixture, this should be evident from the similarities of the two reference hydrocarbons. Although flame speed does play a minor part, there are many other factors that are far more important. ( such as compression ratio, stoichiometry, combustion chamber shape, chemical structure of the fuel, presence of antiknock additives, number and position of spark plugs, turbulence etc.) Flame speed does not correlate with octane."

http://www.repairfaq.org/filipg/AUTO...l#GASOLINE_004

 

Ethanol increases fuel consumption per HP delivered because it contains less "stored energy" than MTBE did. MTBE was the additive that was used before Ethanol in order to "increase the octane". The biggest reason for the government enforcing the switch from MTBE to Ethanol is the MTBE from exhaust emissions was getting into the environment and polluting water supplies, etc.

Ethanol is very high octane compared to normal unleaded gas. However, it is inferior when you compare it's explosiveness to dino fuels. So, it's slightly better for the environment because the CO2 created during combustion is slightly offset by the plants used to make it. However, it's not perfect. If I'm not mistaken, it has the nasty side effect of significantly increasing your HC emissions vs. MTBE unleaded.

On modern cars the difference may be minimal, but on a car with carburettors it makes a huge difference. Not to mention the Ethanol has adverse effects on rubber fuel lines on most older cars. When I was forced into using Ethanol laced fuels, I had to replace all the rubber fuel lines with new stuff that's been formulated to handle the Ethanol.

 

Minor ping is fine, I believe it even says so in the owner's manual. Knock is something entirely different.

 

if your engine every so often pings and allows it to do so, this will dramatically decrease engine like as it will eat away at your pistons eventually, no?

I just got 550 kms on 94 and it was a 52L fill up. also I was driving it hard (catching a ferry, read the WRX vs lancer in the lancer gen. forum)

 

The odd ping is normal, it can simply be the result of slight variations in gasoline with each tank/injector cycle. Prolonged knock kills engines. There's no point in runnning 94 in a car designed for 87, you might as well just send me the money. 550 km is insanely bad fuel mileage for a car like that, hell that's the kind of fuel mileage I get.

 

well, do you drive a 08 lancer? then no its not that bad for this car. other posts for fuel mileage on this car range anywhere from 380 kms to 550. out of 50 L or so. so 10L per 100kms and better isn't bad since most of us have a lead foot. I like my premium, its 2$ extra a tank big whoopdi dooo.

My 1987 honda prelude got 400 kms per tank ( roughly the same size) so 150 kms more out of the same engine displacement is good for me.

 

Are you somehow suggesting that the 08 Mitsubishi Lancer is capible of doing what no other car is capible of doing, insomuch as determining the grade of octane and adjusting the timing to take full advantage of it? I personally don't need to drive an 08 to know that what you are suggesting is BS. Higher end vechicles don't have that ability, what makes you think the Mitsubishi would be different?

Using premium gas in an economy car has already been throughly debunked in all other gas threads and actual research. Your car was designed to take advantage to burn 87 octane. As has been said, all you are doing by using higher octane is wasting gas. If you feel differently then you are welcome to your thoughts.

Also, if you guys want to save gas loose the lead foot. By driving conservativly you will save at the pump, depending on how much you drive up to 50-100 bucks a year!

 

Exactly, there isn't a car in the world that actually figures out what octane you put in and builds a fuel and ignition map around it. Plenty of cars have the ability to retard timing if they detect knock, but that's a fail safe mechanism and sure as hell isn't fool proof. The only way a car could take advantage of higher octane would be to make the map more aggressive but that would also be insanely risky; what happens if the car is constantly adding timing, getting knock and then retarding the timing again? Like I said, that gas mileage is horrible. I have almost 100 hp on you and I get that kind of gas mileage.