Does E85 lower your MPG?

Does running E85 fuel with up to 85% ethanol, actually lower your MPG? That was the question this week from Kirsten in Oregon. (You can hear her call right here-- it's second in the segment.) Her Flex-Fuel Chrysler Town and Country is getting lousy mileage and rough running rough-- but only when she uses E85.

Tom and Ray claimed that lower MPG is to be expected, since E85 has fewer BTUs than old-fashioned gas. They also claim the same thing in our Car Talk Guide to Alternative Fuels.

What do you think? If you drive a flex-fuel vehicle, what's your experience? We want to hear from you.

Share your thoughts right here-- and thanks.

Of course it does. It’s been shown to reduce it by 30% or so (exactly in line with the loss in BTU content), in several instrumented, documented tests (as opposed to “This is what I got” stories).

No one has to own an E85 vehicle to know the score. Our own EPA states it boldly at Her very own 3.3L T&C gets city/highway mileage of 17/24 with gasoline and 12/17 with E85. You are absolutely, positively, 100% guaranteed to get worse mileage with E85. If you want to thank someone for this, contact your ever-vigilant toadie, lap-dog, sycophant Corn-State politico that fought so hard to take food out of peoples mouths so that it could be sold for MORE and end up in your tank.


We all know it garners less mpg. And yet it costs less per g. There is none around here at all so don’t know the price comparison.

My personal question is thus ; Which fuel choice actualy costs the owner less money out of pocket ?

Spending less each fill up but filling up more times ? Or filling up less often at a few more dollars ?

One price camparison I found shows to cost less to burn gasoline.
1000 miles @ 17mpg e85 = 58.52 gal used @ $2.09 gal = $122.93
1000 miles @ 24mpg gas = 41.67 gal used @ $2.58 gal (or less in Des Moines, Iowa) = $107.00

Looks like e85 also lowers your r.p.m…remaining pocket money

I seen a few stickers on new GM vehicles with flex fuel that states you get X amount of miles per tank with regular fuel and Y amount per tank with E85, where Y >= 100 miles

I don’t totally disagree with your stance, but I have to point out that the corn that is used to make ethanol is not what you get in the grocery store. By time you “see” that corn, it has been smashed, mushed, fractionated, and modified beyond recognition.

Corn and ethanol are both subsidized directly. Oil and gasoline are subsidized in the cost of entanglements overseas. You win some, you lose some.

Hi Guys,
I am something of a fuels geek (you guys are car geeks, you get the picture). You were partly correct in telling Kirsten that her lower mpg was because of the lower btu/lb of E85 - really it is the lower btu/gallon that matters. So for the consumer cost is everything. E85 needs to cost less, but how much less depends on how much ethanol is in the FFV fuel, it should actually never be 85%, and in the winter is as low as 70% in some locations to increase the vapor pressure to the point where you can start the car. We need to stop calling this fuel E85 but rather something like FFV fuel or blended fuel ethanol.

As for the rough driving, what is called driveability is a complex function of the volatility and boiling point distribution of the gasoline. The ASTM spec for gasoline (D4814) varies these parameters over the seasons and in different locations to ensure good driveability. For FFV fuel the spec is D5798, which also varies will time of year and location. It was designed at a time with gasoline used for blending was allowed to have higher vapor pressure. Today, gasoline vapor pressure is regulated to be so low (to reduce fuel evaporation from the car - an air pollution issue), that you cannot just take legal gasoline and blend it with ethanol to make FFV fuel that meets the volatility requirements - although that is what everyone still does. So FFV fuel gives poor driveability in many instances. ASTM is working to change its spec to try and help with the situation.

For the oxygen sensor problem, Chrysler uses (I think for this MY) what is called a virtual fuel composition sensor. That is they use the oxygen sensor signal and other signals to the engine’s computer (fueling rate for a given engine power output, for example) to infer the fuel composition. Apparently some part of this is not working correctly in her car - although it runs fine on gasoline so the car is apparently compensating.

I see arguments below against using corn for fuel, do some research on the facts on that, you might decide it is a workable if not perfect idea. With the big run up in ethanol production over the past 5 years, corn exports have remained constant, corn acres have varied up and down by about 5 or 10%, and rain forest destruction in Brazil has gone up or down based on local factors - not demand for ag commodities. Corn productivity in the US, on the other hand has done nothing but go up - allowing more ethanol to be produced.

Cars designed to run E85 will achieve their EPA rated gas mileage figures. using E85 in a car not designed for E85,well that’s a whole new thread.

There is X amount of land available to grow food. If some of that X amount of land is used to grow corn for fuel, then that amount of land is not available to grow food. How does that not reduce the amount of available food?
The real problem here is that it takes more fuel to produce and convert the corn into fuel than you get back out of it. How is that not stupid?

Yes, but they are rated for higher mileage when running off of E10 than E85.

We’ve noticed that E85 does lower our mileage. We now avoid using it.
Steve in CO

What does the manufacture have to say about using E10 in a car designed for E85 and has the EPA tested E85 vehicles running E10?

AFAIK, all cars designed for E85 have fuel sensors and can run on any mix from E85 on down.

You mean “on up” as E85 is as far down as it gets from unaduletrated gasoline. Again has the EPA tested E85 cars on fuel other than what they were designed to run on? or have they left it to actual ownwr experience to see what happens?

Why would someone buy a E85 car and then decide to run it on E10 or better? You spend more to get a E85 capable car then decide not to use E85? whats going on here?

No, I meant on down, as in a lower E number such as E10.
I think that some models are only made as flex-fuel models. That’s why someone would buy one, and then run normal gas.

We currently produce a massive number of calories of food in the U.S. and we are already exporting it. It’s subsidized such that it costs $2.50 to produce a bushel of corn that sells for about $1.50.

Where are you getting the claim that it takes more fuel to produce and convert corn? Perhaps they are referring to the fact that natural gas is used to make fertilizer? That can be fixed. Or perhaps they are just referring to the amount of energy used? The process of harvesting and converting need not be fueled by fossil fuels. That would be silly. Corn waste can be burned as fuel. Wind, water, and solar can produce power for the conversion.

The primary upside to ethanol is that it can be carbon neutral. Oil never will be. Burning fossil fuels will increase the amount of carbon above ground.

What would a model have to offer to motivate you to pay more(in many ways) for E85 capability when E85 capability is not something you wanted?

Anyone who really wants to learn more about ethanol should visit the “Alternative Fuels Institute” website. There is a wealth of information there to make informed decisions regarding this fuel.

Well, anyone that wants to read about what the ethanol lobby wants you to hear should visit that web site.