Ive notice when i drive my civic or my fd that when i fill up at 7eleven i get worse gas mileage (drops about 2-4 miles per gallon). i talked to the clerk there and he said they are useing 15% alcohol in the gas, wow that kind of scares me, ive heard good and bad stuff about doing it, from what ive seen and heard is that it will tear up a older motor.I starting going to the gas stations that have the no alcohol signs out front and ive notice im getting my 2-4 mpg back and it runs smoother from what i can tell. Does anyone think or know anything about it or if it will realy damage rotory motors? Is this just an easy way for the oil companies to make more money ? We are already pay 4 dollars and up a gallon

 

You mean ethanol?

 

the clerk told me alcohol, but yea ethanol. I realy dont know that much about it

 

Basics,
You have to burn consideraly more ethanol to equal the same energy of straight gasoline, so the more ethanaol they mix in with the gas the more you have to burn, mileage suffers... that is if you change nothing or have an old non-compensating ecu... now for the positive side of the argument... ethanol has a much higher octane equivalant, which means you should be able to run a more agressive spark advance curve, therfore requiring less throttle for the same amount power...
The auto and oil industries are all for this, cause if you do not have a newer car with an ecu that monitors both A/F and knock and adjusts both fuel and spark timing automatically then you will get poor mileage and buy a new car, or you just bend over and spend more on gas... fortunately if you have a stand alone engine management system then you take it to get re mapped, or you now have an argument and justification for buying one and all is better...

 

Please come again

 

all gas has a certain amount of alcohol in it. some companies may have more or less. the alcohol raises the octane but too much alcohol will corrode. i never really think about that when im buying gas. the only gas i get is shell. i get the best mileage in my 89 r7 and my 06 nissan sentra. 2 completely different cars. im not sure what shell puts in there gas but i noticed that using the same gas all the time is better for your motor. i wouldnt get the gas at a noname stationunless i really needed it.

 

In competition, we use an AFR of 9,1 on ethanol engines which is equivalent to a 14,7 for a normal engine.

 

You'll see more than just ethanol used as the "alcohol" additive in gasolines.

I have seen Methanol, and Isopropyl listed. all at varying percentages. It depends on where you live and who you buy from.

One disadvantage of adding more than trace amounts of alcohol is the amount of water it will absorb. Water will separate in pure gasoline and settle to the bottom of the container, but the alcohol will absorb it and hold in in suspension.

I have seen "gas" so saturated with water that it becomes cloudy. The vehicle, a 40's vintage GPW , would not run on it.

The owner said the gas was at most, two weeks old. You could not see through a pint jar of it.