# e85 fuel **URL:** \ **Category:** Factual Questions\ **Created:** [March 23, 2009, 2:32am UTC](https://boards.straightdope.com/t/e85-fuel/490415 "2009-03-23T02:32:42Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![jonthebuckeyenut](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@jonthebuckeyenut](https://boards.straightdope.com/u/jonthebuckeyenut)\ **Post date:** [March 23, 2009, 2:32am UTC](https://boards.straightdope.com/t/e85-fuel/490415/1 "2009-03-23T02:32:42Z")
I inadvertently used e85 fuel in my non-flex fuel vehicle and it seemed to run just fine and cheaper than fuels with 10% ethanol. What are the consequences if i continue to use e85 in my 99 ford explorer?? ---
**Author:** ![Mr.Moto](https://avatars.discourse-cdn.com/v4/letter/m/9de0a6/32.png) [@Mr.Moto](https://boards.straightdope.com/u/Mr.Moto)\ **Post date:** [March 23, 2009, 2:41am UTC](https://boards.straightdope.com/t/e85-fuel/490415/2 "2009-03-23T02:41:39Z")
There may be consequences with a rough idle, as the oxygen requirements are different. There may be issues with engine life, as the fuel is corrosive to engines not built for it. You will get worse mileage. There is less energy in the fuel than in gasoline gallon for gallon. ---
**Author:** ![jonthebuckeyenut](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@jonthebuckeyenut](https://boards.straightdope.com/u/jonthebuckeyenut)\ **Post date:** [March 23, 2009, 2:49am UTC](https://boards.straightdope.com/t/e85-fuel/490415/3 "2009-03-23T02:49:30Z")
I didnt notice less fuel efficiency, I did notice 6 dollars weekly savings. Can I use it with a fuel treatment? ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [March 23, 2009, 2:53am UTC](https://boards.straightdope.com/t/e85-fuel/490415/4 "2009-03-23T02:53:23Z")
How much did you put in? Chances are you didn’t put enough in to get the total ethanol concentration in your gas tank high enough to cause problems, but if you continue to put more E85 in, eventually you will get the concentration high enough to have problems. You’ll probably see running issues with high ethanol concentration in a non flex fuel vehicle, but you’ll also over time cause damage to the rubber components in your fuel system. ---
**Author:** ![jonthebuckeyenut](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@jonthebuckeyenut](https://boards.straightdope.com/u/jonthebuckeyenut)\ **Post date:** [March 23, 2009, 3:14am UTC](https://boards.straightdope.com/t/e85-fuel/490415/5 "2009-03-23T03:14:13Z")
I i have a 21 gallon tank and did it twice before i noticed the disclaimer that this is not gasoline, lol, each time at least 19 gallons. I hate to fuel up, so I wait until the need is dire. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 23, 2009, 4:05am UTC](https://boards.straightdope.com/t/e85-fuel/490415/6 "2009-03-23T04:05:31Z")
> [@jonthebuckeyenut](#): > > I didnt notice less fuel efficiency, I did notice 6 dollars weekly savings. 76,000 = BTU of energy in a gallon of ethanol 116,090 = BTU of energy in a gallon of gasoline Gasoline around here is 10 percent ethanol (I guess you could call it E10). That means a gallon of it contains (0.9 x 116,090)+(0.1 x 76,000) or 112,081 BTU. A gallon of E85 is (0.15 x 116,090)+(0.85 x 76,000) or 82,013 BTU. 82,013/112,081 = 0.73 That means E85 only has 73 percent as much energy as the regular gasoline mix they use around here (ymmv, literally, in areas with slightly different ethanol levels). Unless your car was running really poorly on regular gasoline and somehow runs better on E85, there had to be a mileage drop. You may not have noticed it, but it had to be there. If the cost per gallon is 27 percent cheaper for the E85, and the engine is equally as good at extracting the energy from E85 as it is from gasoline, then you’ll break even in the long run. If the cost per gallon is more than 27 percent cheaper, then you’ll save money with E85. If it’s less than 27 percent cheaper, then you are actually losing money in the long run, even though each full tank of gas is cheaper. There are a couple of other things to consider, though. The first is that you say your car isn’t designed for flex fuels. This means it may not extract the full amount of energy from the E85 because it isn’t designed for it, which will make it even less efficient on E85. The other issue is that if your car isn’t designed for it, the E85 will slowly eat away at your engine and fuel system. The damage won’t be noticeable in the short term, but in the long term you could cause yourself some very hefty repair bills. ---
**Author:** ![FRDE](https://avatars.discourse-cdn.com/v4/letter/f/e68b1a/32.png) [@FRDE](https://boards.straightdope.com/u/FRDE)\ **Post date:** [March 23, 2009, 10:25am UTC](https://boards.straightdope.com/t/e85-fuel/490415/7 "2009-03-23T10:25:17Z")
Could it be that the 15% ethanol raised the octane of the fuel ? (ie: prevented it exploding prematurely 🙂 ) That would explain the improved mileage. As for engine damage, the fuel itself touches very few engine components (we are talking 4 stroke, not 2 stroke mix or Wankel) so is it certain that there would be damage ? ---
**Author:** ![luvrbcs](https://avatars.discourse-cdn.com/v4/letter/l/7c8e57/32.png) [@luvrbcs](https://boards.straightdope.com/u/luvrbcs)\ **Post date:** [March 23, 2009, 12:39pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/8 "2009-03-23T12:39:12Z")
Here is what it can do… > **[Problems and Disadvantages of Ethanol Alcohol Blend Gasolines - E10.](http://www.fuel-testers.com/ethanol_problems_damage.html)** > > Problems and damage from ethanol alcohol blend fuels. Fuel Testers educates and helps the public protect their engines from E10 gasoline. ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [March 23, 2009, 12:41pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/9 "2009-03-23T12:41:19Z")
> [@FRDE](#): > > Could it be that the 15% ethanol raised the octane of the fuel ? > > (ie: prevented it exploding prematurely 🙂 ) > > That would explain the improved mileage. Highly unlikely. Ethanol _does_ have a higher octane rating than gasoline (and E85 is 85% ethanol, not 15% ethanol). However, high-octane fuel doesn’t in general give you better gas mileage. The exception is when your vehicle is _designed_ for higher octane fuel. In that case, using _lower_-octane fuel will decrease mileage because the engine controller will reset spark timing to compensate, resulting in poorer performance. [Cecil’s column.](http://www.straightdope.com/columns/read/2565/whats-the-difference-between-premium-and-regular-gas) > [@FRDE](#): > > As for engine damage, the fuel itself touches very few engine components (we are talking 4 stroke, not 2 stroke mix or Wankel) so is it certain that there would be damage ? Not so much to the engine itself, but alcohol isn’t compatible with a lot of things in the fuel delivery system of a normal gasoline car–seals and other plastic parts are not compatible, and it corrodes plain steel and aluminum. The most likely candidates for failure are the fuel pump cutting out or an injector seizing. ---
**Author:** ![old\_yellow\_tz](https://avatars.discourse-cdn.com/v4/letter/o/a8b319/32.png) [@old\_yellow\_tz](https://boards.straightdope.com/u/old_yellow_tz)\ **Post date:** [March 23, 2009, 2:42pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/10 "2009-03-23T14:42:00Z")
Stochiometric mixture for gasoline is 14.7:1, For E85 it is 9.8:1, So if you’re running E85 in a gasoline engine, you’re technically running 34% lean(!!!). Since you have an oxygen sensor, the ECU may compensate but usually it is limited to 10-15% enrichment. $6/week is pretty meek compared to the bill of a hole-in-the-piston repair or all the other corrosive damages already mentioned. Thread at your own risk. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [March 23, 2009, 3:17pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/11 "2009-03-23T15:17:53Z")
Basically, accidentally filling up once or twice with E-85 won’t have a noticeable effect on engine wear. Because it’s a higher octane fuel, it may make a mistimed engine run a little better, but there would also be a lowering of gas milage. As noted, unless the engine’s parts are designed for E-85’s different chemistry, long-term use can definitely lead to some parts failing prematurely. Best to stick with standard unleaded. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [March 24, 2009, 1:01pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/12 "2009-03-24T13:01:46Z")
Bizarrely, last Friday (March 20th) I saw a local station selling 87-octange regular unleaded for $2.119, and E85 for $2.399. Why on EARTH would 85% ethanol be almost thirty cents per gallon MORE than regular gasoline? ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [March 24, 2009, 1:26pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/13 "2009-03-24T13:26:38Z")
Probably because it costs more to make. A better question would be, “Why on EARTH would anyone _buy_ 85% ethanol if it costs almost thirty cents per gallon MORE than regular gasoline?” (Not an answer to the question, but E85 does have a high octane rating, so you might compare the price to premium also.) ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [March 24, 2009, 2:12pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/14 "2009-03-24T14:12:57Z")
> [@zut](#): > > Probably because it costs more to make. A better question would be, “Why on EARTH would anyone _buy_ 85% ethanol if it costs almost thirty cents per gallon MORE than regular gasoline?” > > (Not an answer to the question, but E85 does have a high octane rating, so you might compare the price to premium also.) Well, yeah, but that’s my point. It’s always been at least $0.10 cheaper per gallon than the cheapest 10-15% ethanol-added gasoline before, because you get crappy mileage with E85 compared to the regular 10-15% ethanol mixes. So how can they possibly be selling it for significantly MORE than ordinary gas? Who would buy it? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [March 24, 2009, 3:16pm UTC](https://boards.straightdope.com/t/e85-fuel/490415/15 "2009-03-24T15:16:06Z")
> [@chorpler](#): > > Well, yeah, but that’s my point. It’s always been at least $0.10 cheaper per gallon than the cheapest 10-15% ethanol-added gasoline before, because you get crappy mileage with E85 compared to the regular 10-15% ethanol mixes. So how can they possibly be selling it for significantly MORE than ordinary gas? Who would buy it? Nobody right now. But at one point, it was cheaper in certain areas of the country. It also may be more generally cheaper in the future, with or without government subsidy. In general, I don’t mind seeing cars being made with flex-fuel capability. It doesn’t hamper the ability to use gasoline, and provides a ramp up to possible use of cellulosic ethanol in the future. Corn or sugar cane based ethanol is a stopgap at best, but if we can get cellulosic ethanol production at commercial levels, it might provide one of the pathways off the oil teat, and it will be a big help to have a lot of ethanol burners already out there. If it DOESN’T pan out, it’s some wasted cost and effort for the manufacturers, but not an enormous amount.