How is gas mileage affected by using fuel with ethanol added? The number I have heard most often is about a 2% reduction in mileage for a 15% blend.

In our area of the country it’s all 10% blend. Typically it seems to make about a 1 to 2 mpg difference.

Somone here will surely post the differences in BTUs and do the math, but that’s what the reality seems to be.

The math suggests that the difference should be minimal (2% or so) but the reality for most cars that I have been aware of is that it is more like 5-10%). On the other hand, I used to drive a carbureted Toyota for which I tracked the mileage for every tank over several years. That car actually got BETTER gas mileage in winter with oxygenated fuel (using MTBE rather than ethanol - also has lower energy density). The car had no air conditioner, so that would not explain the difference. Clearly there is more physics at work here than the just the energy density of the fuel.

My experience over the past year with E10 (10% ethanol) is approximately a 10% reduction if fuel mileage in both of my cars (a Subaru and an Acura, both 4-cylinder) when using E10, or about 2 - 3 mpg.

I record and track fuel mileage with every tankful, and have noticed this difference in both highway and city driving in all kinds of weather. My tires are always kept at or slightly above the recommended inflation pressure, and I follow the maintenance schedule for each car.

In my area it’s becoming very difficult to find gas that does NOT have 10% ethanol. I prefer straight gasoline when I can find it, but I won’t go out of my way to get it.

So if that stuff reduces mileage 10% and it is 10% of the total, it is adding nothing to the operation of the car. It is really using oil based products to produce it and distribute it, while doing thing. I think I would rather save the corn for eating.

I wholeheartedly agree. I feel confident in suggesting that there’s more “green” politics and agricultural industry lobbying than actual science in the ethenol scam.

Politics and lobbying…they go together like bacon and eggs. Guess who always pays?

Me, because E10 is the same price as straight gasoline, but I get fewer miles per gallon. Corn-based ethanol as an automotive fuel is a scam.

The only way to find out the mileage reduction is to crunch the data from your own vehicle the way I did mine, friends, and family. The results of every vehicle will be slightly different.
My cars are 4.3s. I get 16 mpg with ethanol and 20 mpg with gasoline.
A difference of 4 mpg. My gas tank is 20 gallons. That means I can go 80 miles further with gasoline for a few pennies per gallon. To find out how many gallons I’m saving per TANK, divide the 80 miles by 20 mpg which is 4 gallons.
To find out how much money I’m saving by using gasoline, multiply the 4 gallons by the cost of a gallon of gasoline (currently about $3.40 - $3.50) At $3.40 per gallon I’m saving $13.60 per tank by using gasoline. To find out how much per gallon I’m saving divide the $13.60 by a 20 gallon tank which comes out to
.68 cents per gallon. This will fluctuate with each car and the rise and fall of prices. So if your car has a 3 mpg difference you save .51 cents a gallon, 2 mpg difference, you save .34 cents a gallon by using gasoline. One mpg difference, .17 cents a gallon.
Its pretty obvious the the 2% reduction in mileage is REALLY 20%.
Its my opinion that once the gasoline arrives at the distributors where the ethanol is added, there is no regulations or overseers to monitor how much ethanol is mixed.
The more ethanol, the greater the savings to the distributors. Thats the only way I can see how 10% ethanol can waste 20% in mpg. Ethanol as a renewable source of alternative fuel should cause the cost of a gallon of 10% ethanol to drop by 30% not 3% and it doesn’t as you can see. Its become a political issue and a national scam.
Back to your question, if you’re already using ethanol, get your mpg.
Find a major oil company distributor ie., Shell, Chevron, Texico, Phillips,
Exxon, Amaco/BP and if there are no “ethanol labels” on the pumps, go in and ask the mgr. if they are selling ethanol products… If they are not, get the mpg and check the results… If the mpg are the same, go to another major oil distributor and try again. (Sometimes the stations themselves don’t know what their
tanks are filled with.)
Stations are switching to ethanol for a couple of reasons…1. Laws have been passed where pretty soon 10% ethanol is mandated to be mixed with gasoline.
2. Stations are competing for customers to come in and buy the coke a colas and chips, ie., products which they make most of their profit margines from.
Good luck with your data research. Hope it matches mine.

10% is mandated everywhere around here. There’s no way to compare by actual testing. I’m just basing my answer on how much it seems to have affected my mileage when the change was made and discussions with friends on the subject.

Without testing on a lab where all the other variables can be controlled, all one can do is use either anecdotal evidence or do the math…which, as Manolito said, doesn’t seem to really work that well. There are variables driving the programs in the ECU that are probably affected in suttle ways that when added up and applied to the task of accelerating a 1-1/2 or 2 ton machine through various environments probably cause more of an effect than simply the change of BTUs in the fuel would suggest it should. That’d be my theory.

In many parts of the country MTBE is mo longer allowed to raise the octane rating. The oil companies must use ethanol. Older gas storage tanks in the ground can develop leaks and leaking gasoline finds it’s way into the ground water.

My 2004 F150 gets better than EPA estimated city (16 vrs 14) using blended gas.(4.2l).

The mileage is satisfactory, on to other issues.