Join Our Ford Truck Forum Today

Document your Ford truck project here and inspire others!

Fuel mileage E85

I have a 2008 f 150 just got not to long ago it is a flex fuel. ..Can someone tell me what mileage I can get with it compared to regular...I have 5.4 window sticker says 19 highway 13 in town..Am I gonna get better or worse with E 85
 

Lost

PA Chapter leader
3,288
33
central PA
Worse All our company cars lost about 2MPG
 

CowboyBilly9Mile

Charter Member
7,103
404
E WA state.
By volume, alcohol contains 2/3 the energy that pure, 100% gasoline does. So let that be your guide as you crank out a comparison between E0 and E85.
 

Fellro

Moderator
Staff member
The engine is designed for running regular gasoline. As such, it does not get as good of mileage from it. In order to do well with the E85, you would need higher compression than what gasoline allows. This dual fuel garbage doesn't work with propane, nor does it work with E85. The properties just don't trade off well, and mileage will suffer.
 

polarbear

just growing older not up
12,878
605
Boring, Oregon
The only real advantage the flex fuel setups have, as I understand it, are fittings and fuel lines designed to tolerate the corrosive qualities of E85 fuel. We don't have this choice in Oregon- everything's E85.
 
I'm an self confessed alternative fuel freak who has messed around with diy hydrogen hybrid system's and am currently experimenting with ethanol in my spare time ..... i'm pretty hung up on the advantages of ethanol especially as originally promoted by Henry Ford's Model farm distilleries.


By volume, alcohol contains 2/3 the energy that pure, 100% gasoline does. So let that be your guide as you crank out a comparison between E0 and E85.

The trouble with that energy calculation Bill is that it is based on a BTU measurement ..... BTU stands for British Thermal Unit and is a measure of heat energy not Combustible energy - eg a stick of dynamite only has 2000 btu whereas a gal of gasoline has 125000 btu . Even though the dynamite has only 2000 btu it has an explosive energy many times greater than the gallon of gas..... It's all in the way you harness the available energy that counts towards the final result

The engine is designed for running regular gasoline. As such, it does not get as good of mileage from it. In order to do well with the E85, you would need higher compression than what gasoline allows. This dual fuel garbage doesn't work with propane, nor does it work with E85. The properties just don't trade off well, and mileage will suffer.

I couldn't agree more Roger - Gas has a stoichiometric requirement of 14.7:1 whereas ethanol has a requirement of around 9:1 with a fluctuating requirement in between those figures depending on percentage of gas in the ethanol. With Flex Fuel systems there is basically two maps in the ecu that change (advance) the timing and increase the fuel flow (pressure or volume) if E85 is detected in the system (the really clever systems can work with any percentage up to E100 although this is mostly done in Brazil). Gasoline typically burns in an engine at around 25 - 28% efficiency - if you try to increase the compression ratio to get better efficiency you'll develop pinging and knocking. Ethanol however can get up to 38% efficiency as the compression ratio can and has been raised up to 17:1 before pinging occurred .... of course spark ignition is no longer used at those levels. Just from anecdotal evidence I've read and people I've talked to 11.5:1 seems to be the minimum compression ratio that you want to build an ethanol to so as to achieve the same or better efficiency as a modern gas engine. There are currently engines under development that are aiming for a variable compression ratio and if they ever get off the ground then pairing those up with a flex fuel system will give you the best of both worlds imo.
 

fatherdoug

Tonto Papadapolous
Good read, Mark. Thank you. How does the ECU determine what type of fuel is being fed to the engine?
 

Fellro

Moderator
Staff member
There is a sensor in the fuel line that detects the level of alcohol in the fuel. I know there is always chatter about the corrosiveness of E85, but I have run E10 all of my driving life and have yet to see it. The tank on my 83 Trans Am is as clean on the inside as the day it was made, and I have run E85 through it as well. I also haven't seen any unusual deterioration of the fuel lines and seals, even on a car that had gone 5000 miles shy of 400,000 miles running exclusively E10 and occasionally some E85. I changed the injectors at 250,000 miles as they were simply worn out.
 
Thanks for clearing that up...reason I asked a guy brought a 2010 mixed e 85 with regular gas which was at half tank and he tryed telling me he got 22 mpg....Mine is flex fuel also so before I added e85 wanted to see what milage would be...I'm sticking with regular..
 

CowboyBilly9Mile

Charter Member
7,103
404
E WA state.
The trouble with that energy calculation Bill is that it is based on a BTU measurement ..... BTU stands for British Thermal Unit and is a measure of heat energy not Combustible energy - eg a stick of dynamite only has 2000 btu whereas a gal of gasoline has 125000 btu . Even though the dynamite has only 2000 btu it has an explosive energy many times greater than the gallon of gas..... It's all in the way you harness the available energy that counts towards the final result

That is true, what I mentioned is based on thermal energy content rather than volumetric expansion. Which leads back to the engine itself, the Otto cycle really works most effectively with the expansion of the gas rather than other things. There's a production cost issue with the alcohol too, this trickles back to the pump.


------------------------------

Something else to think about Alan, and that is how corn farmers are subsidized by the US gov't, and as such, they can't get the American public to use enough of the stuff. Wayyyyyy back in time, it was animal feed, then in the early 80's it (High Fructose Corn Syrup, AKA, HFCS, the satan of sweeteners) became a HIGHLY used substitute for real sugar, and now roughly 10 years ago, Bush #2 signed a renewable energy act requiring that "up to" 10% of the content in fuel be alcohol. Ever read the gas pump carefully? The E10 pump will read, "may contain up to 10% alcohol". Nice scam, the consumer doesn't know what their money is buying. Would you buy a bottle of booze if it said, "may contain up to 80 proof"? As for the HFCS, real sugar contains 50% fructose and 50% glucose; HFCS does not. Many researchers believe the body metabolizes it differently than real sugar, and that the result is that HFCS promotes fat tummys. Right or wrong, just look at pictures of people in the 60's and 70's then look at all the fatties today, then draw your conclusion (or read more into it). And then, ask yourself if you want to support gov't subsidized production of a product with questionable health consequences to American and curiously enough, rusty gas tanks on motorcycles, lawnmowers, etc etc. IMO, if the corn farmers could convince the water districts all across America that adding it to tap water was of benefit to people, they would do so. They fiercely guard production of that corn like a hawk and have no trouble saying whatever needs to be said to defend production.
 
Last edited:
the above is probably all true.. but wanted to throw another thing ive heard with switching between the 2.. If the vehicle has a lot of miles on it and only run Regular Gasoline through it all its life I would be leary of suddenly throwing E-85 into it. Have heard and read alot of reports about how e-85 will strip the varnish off the fuel system, valves, cylinder walls ect ect. gasoline leaves behind when its run through. When it strips that off it can plug up the fuel filters, injectors, and supposedly leave the burned deposits that were stripped from the cyl walls and valves in the cylinder..

But like I said thats the biggest thing ive heard about e-85 in flex fueled vehicles.. dont know how true it is. but wanted to throw it out there..
 

fatherdoug

Tonto Papadapolous
There is a sensor in the fuel line that detects the level of alcohol in the fuel. I know there is always chatter about the corrosiveness of E85, but I have run E10 all of my driving life and have yet to see it. The tank on my 83 Trans Am is as clean on the inside as the day it was made, and I have run E85 through it as well. I also haven't seen any unusual deterioration of the fuel lines and seals, even on a car that had gone 5000 miles shy of 400,000 miles running exclusively E10 and occasionally some E85. I changed the injectors at 250,000 miles as they were simply worn out.

Thank you. Is the alcohol detected by difference in density? Enquiring minds want to know. :D
 

Fellro

Moderator
Staff member
That is my understanding, yes.

Actually, thermodynamically, the Otto cycle is more efficient when the compression is higher. The pressure difference is increased, thereby getting more back from it. That is also why diesels tend to be more efficient. It isn't as much the energy content as it is the pressure differences. It doesn't take as much bang when you are already at a higher pressure.
 
Last edited:
Top