Originally Posted by justnspace

ethanol in fuel will decrease fuel economy.

if you can find premium fuel without ethanol, you'll see your MPG climb!

Originally Posted by fujiteam

Is 93 less fuel effecient?

Originally Posted by losiglow

This conversation is old hat , but it's fun to talk about anyway. It's this easy:

1st - Yes, many have experienced this phenomenon, that is, a consistent 10% decrease in MPG from the 10% etOH in gasoline. From a chemical standpoint, etOH contains only a fraction of the energy that is found is gasoline. Therefore, via simply chemistry, you're going to suffer an equal mileage loss equivilant to the reduced energy potential from added etOH. Usually it's less than 10% since etOH contains some energy (just not nearly as much as gasoline). So while it burns much cleaner than gasoline, you're simply having to use more gasoline to get the same result yielding no actual pollution reduction.

2nd - The reason etOh is in gasoline is NOT because it's somehow better for the environment. After accounting for milage loss, we're breaking even (actually, not even that, see "3rd"). etOH is in gasoline because of the ethanol/corn lobby convincing the government to add it.

3rd - Adding etOH is actually worse for the environment because of the energy (in the form of fossil fuels - coal and oil) required to manufacture ethanol.

It's a lose/lose for the american consumer but a great way for government lobbiests to line their pockets. It's a steaming pile of horse

Originally Posted by I hate cars

Agreed. As usual, a small group of people get rich, we all pay the price, it's the new American way.

Ethanol has about 1/2 the energy content of gasoline so you have to burn twice as much to get the same power. Or said another way you get 1/2 the mpg. The plus is it's led to huge OEM fuel injectors. In the old days, injectors capable of supporting 800hp with only 6 of them idled terribly and had bad street manners; they were not linear through their flow range and did not like the super short pulsewidth required at idle.

Now we have large injectors as OEM equipment on many flex fuel cars that have great street manners and are used as aftermarket injectors on many high hp gasoline engines. Many flex fuel cars also have huge gas tanks which is nice when you run it on gasoline. Some of our work vehicles have 35 gallon tanks where they used to hold 22-ish gallons.

But yeah, if the car has not been optimized for this fuel, mileage sucks. If these a**holes did not lower the octane of the gasoline mixed with ethanol we would have higher octane with 10% ethanol but of course they use a lower octane gasoline and bring the octane back up with the ethanol mix. The ECU would see little to no knock retard and it would advance timing slightly, making up for part of the mpg loss but that's too much to ask for.

As is typical for the government, they do a piss poor job of "research", not that they actually care about what's better for us or the environment. Sure, the ethanol mix is ever so slightly cleaner through the tailpipe which is the selling point to the general public. However, you're burning a larger volume of it due to the lower BTU content. It also takes a ton of hydrocarbon fuel to produce Ethanol. In the end it's worse for the environment but hey, it's cleaner out the tailpipe and leaving out all of the other facts makes it easy to sell to the public. Kind of like electric cars. They have "zero emissions". I guess that's true, the car puts out no emissions.... but the coal burning power plant 100 miles away that supplied the energy puts out a whole hell of a lot more pollutants than a modern ULEV or PZEV car does for the same power.

My TL with the 3rd cat removed had it's first official smog test which is it's second test. The first one when it had a few thousand miles on it had almost zero hydrocarbons. This last one with 120,000 miles had absolutely zero hydrocarbons. While that's not the only pollutant we're concerned with, show me a coal burning power plant that puts out that low of emissions for a given power output. Ethanol mix in the fuel is not needed nor is it good for the car or the environment. If they actually cared about mpg they would have left the gasoline's octane the same and let the car manufacturers take advantage of the 95-96 octane with more ignition timing to get back some of the losses.

Another problem with ethanol is it can cause the car to run leaner. The ECU has a target AFR to hit under various conditions and it uses the 02 sensors to make sure it's hitting that target. Introduce the ethanol mix without changing the target and you end up with a lean condition...... Say it's shooting for 14.7:1, stoich for gasoline and it hits the target AFR as it should. The ECU and 02 sensors are doing their job just fine. The problem is, 14.7 is very lean for ethanol. With only a 10% mix the car still runs and it runs acceptable but it most definitely is not going to run at it's best.

I'm going off topic but I believe diesel is the best thing we currently have, at least in the near future. Emissions are now low. They no longer sound like a diesel or smell like a diesel or have NVH like a diesel. My friend's Jetta TDI gets 44mpg in town and that's not driving it easy. He's hit 59-60mpg on the freeway a couple times driving it nicely. No batteries and no coal burning power plants to supply the power.

Originally Posted by fujiteam

Last weekend I was at a station that had 87, 89, 91, and 93. I put the 93 in and got the same ~10% improvement in fuel economy. I had first thought the ethanol was giving me the benifit. I wonder now if it is worth it for me to find a station with 91 for my regular fill ups. Maybe with 91 I can hit the 500 miles on a tank mark.

Originally Posted by fujiteam

My expierance says I should seek out 91 octane over 93 assuming 91 is cheaper and I am not going out of my way.

Originally Posted by fujiteam

I have gone through a lot of the fuel economy threads and have not seen one mention octane differences.

I normally put in 93 because my gas station has 87 and 93. Occasionaly when I drive form Rochester NY to Springfield, MA I fill up with 91 octane 0% ethanol. Usually I get about 10% better fuel economy than when I do the same trip with 93.

Last weekend I was at a station that had 87, 89, 91, and 93. I put the 93 in and got the same ~10% improvement in fuel economy. I had first thought the ethanol was giving me the benifit. I wonder now if it is worth it for me to find a station with 91 for my regular fill ups. Maybe with 91 I can hit the 500 miles on a tank mark.