Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show


Hi! new to the cartalk community and sorry to hear that you guys are going to hang it up! before you go, I have a question about the “up to10% ethanol” at the pump. I thought I noticed a big fall off in our gas mileage in our 2004 Subaru Outback, and first blamed it on our cold winters (you all have a great archived post on that topic!), but now I’m wondering if the addition of ethanol to the gas might be partly to blame. This theory developed when, in Wyoming, I filled up at a station that advertised “no ethanol” and found my mileage to be at my new-car levels; next fill up, on the 10% ethanol stuff, my mileage dropped about 20%. I know that, in Wyoming, your mileage will vary depending on which direction you are driving (east or with the wind vs. west or against the wind), but these two fill ups were both heading east. Long story short (too late!), I’m starting to think that the ethanol mix is really hurting my mileage. Is this just my imagination, or have other folks noticed the same thing?

I know the ethanol mix is supposed to be better for the environment, but if I have to burn five tanks of gas to cover the same miles that four tanks used to cover (my math is probably backwards there), am I still helping the environment?



No, but you’re contributing to support the wealthy agricultural conglomerates…oops, I mean the “poor farmeres”.

Gasoline provides more energy when it burns than ethanol does. You can reasonably expect lower gas mileage with E10 than gas with no ethanol. But gasoline without ethanol needs another chemical to increase the octane level. This is often MTBE. But MTBE can be a long-lived source of ground water pollution. That’s why it is banned in many areas of the US and E10 is used in its place. BTW, gas mileage with E85 is significantly lower than E10 gas. A 2012 Impala using E10 gets 30 MPH highway, 18 MPG city, and 22 MPG combined. The same car using E85 gets 22/13/16. That’s a 29% loss on the highway, 17% loss in the city, and 21% loss overall. Unless you are a titan of one of those agricultural conglomerates that @the_same_mountainbike mentioned, it is hard to understand why anyone would want to use E85.

Because until the federal blend tax credit went away, E85 was a lot cheaper at the pump (if you were bad at math and forgot to add in the public subsidy).

There are a lot of factors to consider, including pollution, mileage and energy.

We have not yet got it all figured out. mileage, power engine life pollution etc all are factors.

I will only suggest that if you look for just one thing like mileage or reduced pollution etc, you are missing other factors. There are lots of trade offs. The manufacturers and dealers will be telling you what you want to hear and will ignore the rest (or likely will not even know about the other factors.

Ethanol STINKS ! Politically, practically and in every other way. Mechanics and makers of additives are reaping huge profits on this crap…even now they are selling the old stuff for $5 a pint for small engines not frequently used, just to avoid it. Until someone comes up with a substitute, read up on it’s effects which for normal driving in a fuel injected car is negligible.

I remember back in the 1980s. Ethanol had just become common in my area. I had been trading with a particular station and began having problems starting my 1978 Oldsmobile when the engine was hot. I would have to crank for quite a while before it would fire up. My wife suggested it might be the gasoline. I switched to a station that didn’t have ethanol added to the gasoline and the problem disappeared. Later on, when all stations sold gasoline with 10% ethanol, I didn’t have the problem with the ethanol blend. The Oldsmobile had a carburetor. The Ford Tempo we had at the time was fuel injected and didn’t have a problem with the ethanol mix.

You are missing the point…When you buy ethanol, the money stays in the United States.

As for a drop in mileage, 3% perhaps, but not 20%…

ADM, loves you.The other day I noticed my neighborhood dealer has started offering straight regular gas alongside the 10% stuff.Tried a tankful (mostly by mistake,didnt realize it was straight gas till I was pumping it) the difference in mileage was dramatic,the Dodge runs good on 10% but the mileage suffers-Kevin

Caddyman…yes but, it “stays in the US” but does it help those intended ?

From “Alternet”

"The problem is that the boom is taking place in the same old agricultural economy, which works to the benefit of those on top: landlords, processors, and companies selling inputs like seeds and fertilizers. It’s agribusiness as usual, and like always, farmers will finish last.

“Initially we all were excited by the high prices,” said Troy Roush, a sixth-generation farmer who grows 2,600 acres of corn in central Indiana. “But the truth is that the farmers won’t keep any of it. There’s an old saying that expenses will always rise to meet revenue. It all gets built in.”

So, IMO the lobby to increase ethanol content is not thinking about the poor farmer who seldom realizes much benefit. Some how, the oil and related companies will max their profits at the expense of the farmer.

Another example of “trickle down”, hidden under the guise of helping the environment.

Well, this is another post in a long line of debates about the mpg loss when driving on 10% ehtanol. Some people, myself included, experience almost no loss in mpg vs straight gasolone, while others report significant losses, like 20%, which theoretically should not be happening. There is just not that much energy difference between straight gas and 10% ethanol…the actual energy difference is only 2 or 3 %.

I would really love to borrow for a month the vehicles of all the people who claim major mpg losses on 10% ethanol and test them myself, because that kind of loss should not be happening.

Like most disagreements, as far as mpg and ethanol is concerned, my experience has lead me to believe that BOTH sides could be right. The effects of ethanol depends on several factors. They include amoung others, humidity, temperature and age of the gasoline. In these varying conditions, I believe two different drivers can experience different outcomes using 10% ethanol. The effects of ethanol on the fuel system is cumulative as well leading to varying outcomes even amongst those who drive in similar conditions that enhance ethanol problems.

Marine motors are subjected to the harshest conditions that bring out the worst in ethanol. In this environment, I have seem first hand, how people in these conditions can also have varying outcomes. I see no reason why these varying outcomes can’t be extrapolated into automotive use.

When in doubt, it ever hurts to use attitives specifically designed for ethanol under conditions that promote ethanol problems.

Personally I notice about 1mpg loss and the vehicle runs like gangbusters on the 10%-Kevin

And, again, it’s worth pointing out that E10 will contain UP TO 10% ethanol but usually less. Here in Boston, if I recall correctly, it’s in the 5-7% range, with seasonal adjustments between winter and summer formulations…

So, E10 isn’t even really 10% ethanol…

Slight correction to what I said above…

E10 IS 10% ethanol, but most gas pumps that say “10% Maximum Ethanol” are probably not dispensing E10, but a lower percentage mix. EPA says it must be at least 5.9% ethanol, so what we get in Boston is 6-7% ethanol.

“Some how, the oil and related companies will max their profits at the expense of the farmer.”

And the independent gas station owner, if these folks still exist. Gas stations can make money if they are in a large enough group to have purchasing power. If the farmers put together a cooperative to sell their products, it might work to their advantage, too. But the coops would have to be very large.

BTW, I recall reading (several years ago) about farm coops that were refining ethanol for a gasoline additive. What happened to them? Are they in business; making money?

The difference in mileage reflects more than the difference in contained energy…it also reflects the difference in the way the fuel burns. And the effect will vary depending on engine design and drivetrain gearing.

20% might be on the high end, but I have no problem believeing hat ethanol-laced gasoline produces more than a 2-3% drop in mileage.

“.The other day I noticed my neighborhood dealer has started offering straight regular gas alongside the 10% stuff.Tried a tankful (mostly by mistake,didnt realize it was straight gas till I was pumping it) the difference in mileage was dramatic,the Dodge runs good on 10% but the mileage suffers-Kevin”

Very few retailers have the storage and plumbing to offer an extra grade of fuel on the pump island…

In coastal areas, marine fuel dealers have been screaming for years to be supplied with ethanol-free fuel…So far, that has not happened…

In Mexico where I live for most of the year, gasoline is 100% gasoline. I notice no difference in mileage when I cross the border…

One gallon of ethanol has 76,000 Btu’s gasoline has 116,090 Btu’s, so in 10 gallon of a 10% ethanol mix you have a total of 1,120.810 Btu’s with 100% gasoline you have 1,160,900 Btu’s, so the mix has about 96.5% of the Btu’s of gasoline so from just a stand point of energy you can expect a 2.5% loss in fuel mileage. Assuming you are really getting 10% ethanol. But as other have said depending on the car or truck involved you can see better or worst fuel mileage. My dad’s truck hated the stuff he was seeing at least a 10% drop in fuel mileage, my truck didn’t seem to care the difference was so small that a headwind would have killed more mileage than ethanol did. Dad truck had a carb and no electronics, my truck had FI knock sensors, etc. and that might have been the diffrence.

Well mine runs great on 10%,but the mileage suffers a bit ,particularly when I use BP,checking it again to make sure it wasnt an anomaly-Kevin P.S the 2 cycle guys say to use midgrade or hi test in chainsaws and such,anything to that?