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Discussion Starter #1
My state sells 70% alcohol fuel (called E85) made from corn. It sells for 23% less than gasoline. Thought I would give it a try. My MPG dropped 7%. No warning lights or any other problems. Are there any potential problems from using this fuel?
 

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I believe that generally any electronic controlled fuel injected vehicle will compensate for the difference in fuel mixture fairly well. If your percentage of alcohol is high enough to throw sensor readings out of bounds then you may get a CEL. In general I wouldn't recommend straight E85 in a vehicle that isn't labelled for it, but, depending on price, you may want to mix it with E10 (our current normal gas).

Only a 7% drop in MPGs would indicate that either your car burns the ethanol pretty efficiently or they're not putting that high of a percentage of ethanol in the E85. E85 should be up to 85% ethanol, but maybe it's not. Was it labelled 70%?

Here's the math on the energy per volume for 85% ethanol vs 10% ethanol:
(unit is MJ/L, but it's the ratio that's important)
E10: (32.4 * 0.9) + (20.9 * 0.1) = 31.25
E85: (32.4 * 0.15) + (20.9 * 0.85) = 22.625

31.25-22.625 / 31.25 = 0.276
or basically, should be a 27.6% drop in energy per volume using E85
 

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The Honda dealership near me says they will not warranty the fuel system etc for cars run on 15% or more gasohol.
 

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Discussion Starter #5
It's labeled as 70% alcohol. I put 5 gallons in the first time, then 9. I was surprised at how little the MPG dropped. As for a warranty, I'm putting it into a 15 year old beater.
 

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You cannot/should not use E85 with any car that is not made for E85.
Agree. E15 cars aren't set up for it. If used long term, it might have some effect on various seals, etc.

I used a tank once in an Echo with no apparent ill effects. I'd dilute the stuff with E15 when it got down to 1/4 tank or so.
 

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Ive mixed 6 gallons of e85 with 4 of regular gas. No problems, but its a gen 2. Currently e85 is 50 cents more still than regular gas. It was cheaper when gas was over 3 bucks a gallon.
 

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Discussion Starter #8
Where I'm at it's 2.39 for E10 gas, 2.79 for E0 and 1.79 for E85. It beats my friends 12.5/1 compression 56 chevy....110 leaded octane fuel is $60 for 5 gallon jug.
 

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70% ethanol

Most vehicles built to use E85 have stainless steal fuel filters and lines as well as larger injectors and higher volume fuel pumps. Alcohol draws in water from the air and tends to corrode fuel systems more than E-free fuels. The reason you get less MPGs with Ethanol blended fuels is they require more fuel flow to equal the BTUs of E-free fuel.
Do a cost per mile comparison with the various fuels to determine which is actually cheaper to use.
My cost per mile difference between E0 and E10 is about equal (.002cents) but the range per tank is greater with E0.
 

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You will use about 20-25% more fuel to achieve the same energy level as gasoline. @ E70 thats probably closer to 15-18%. There is still some residual gasoline in your tank plus the 30% gasoline in the E70 you are using. Your car will certainly be down on power, will throw system too lean code once you max your fuel trims compensation. But the real damage is to come when the alcohol washes out all the soot and sediment from your gas tank and lines into the inlets of the injectors and they clog. Thats when you will burn up pistons/valves from fuel starvation. I have been tuning ethanol EFI engines for 10 years and this is very common for vehicles that have been used on gasoline for some time and then switch. If you intend to do it, do it right and have the ECU remapped/piggyback with larger injectors before you burn up the engine from running way too lean. Ethanol for a naturally aspirated car will never be efficient, save money, make any sense unless your OCTANE LEVEL is otherwise insufficient to deter detonation (high compression pistons) or turbocharged / supercharged.
 

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So what I'm hearing is once I turbo my car, if I have enlarged my injectors or added a 4th one; then mixing in some E85 with 87 octane gasoline may be more economical then buying 91-93 octane gas to prevent knock with a bit of a risk to my fuel filter and fuel line seals. Anyone got the math on what percentage of E85 it would take to bump 87 octane fuel to 90+? Can you just average the octane values, 105 for E85? ie. a 50/50 mix = (105+87)/2 = 96 octane? or is it not linear?
 

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Lets keep in mind that regular gas itself is rather nasty stuff. :D

Johnny, I dont know of those who are boosted who mix regular with e85. They normally go e85 all the way and tune for that setup.
 

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So what I'm hearing is once I turbo my car, if I have enlarged my injectors or added a 4th one; then mixing in some E85 with 87 octane gasoline may be more economical then buying 91-93 octane gas to prevent knock with a bit of a risk to my fuel filter and fuel line seals. Anyone got the math on what percentage of E85 it would take to bump 87 octane fuel to 90+? Can you just average the octane values, 105 for E85? ie. a 50/50 mix = (105+87)/2 = 96 octane? or is it not linear?
Here's the problem. My understanding is that the big power increase in using E85 in a turbo car is being able to wildly advance the timing, then running very high boost. We can't fool with the timing, and I doubt if the internals of this engine will withstand very much boost. Otherwise you're just running low grade fuel that the turbo can't compensate for.

You have to tune for E85, and then you can only run E85, unless you have an ECU that will run more than one map. We don't.

Running bigger injectors will result in running too rich when not under boost, unless you are running an ECU that you can tune. We can't.

I recommend doing a LOT of study before going this far with an Insight. And have a spare engine.

Sam
 

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Sam, did you get the "problem" fixed?
I wish we had more daylight time to run the comparison.
Next time.

Willie
 

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I agree that you'd want the car tuned for it and the map would be different for running a higher ethanol mix vs straight E10. This is possible; it requires a piggyback ECU or map-able control over a 4th injector. How much more fuel the car will need to supply will depend on max boost, current atmospheric pressure, and what percentage of the fuel is ethanol.

I'm not trying to get into a whole discussion here about fuel management or turbo setups. Also I'm not talking about running straight E85 or high levels of boost. I was just saying that a little E85 in the mix can bump up the octane and prevent knock.
 

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Sam, did you get the "problem" fixed?
I wish we had more daylight time to run the comparison.
Next time.

Willie
Not yet. I enjoyed driving your car. Email sent.

Sam
 

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I became interested, did a lot more reading about the use of ethanol in internal combustion engines, and wanted to say a couple more things here.

I'm not going to list a ton of links, but I liked this paper in particular. I think it did a good job of explaining generalized technical information in an easy to read way.


I realized the reason that OP had 70% available to them. Evidently, E85, in colder areas, is switched to E70 in the winter to prevent cold start issues. They leave it "named" E85, but it's 70% ethanol.

About likely MPG loss when running higher ethanol mixtures...
In my overly simplified earlier attempt to figure out the potential MPG loss, I did the math on the energy density difference between E85 and E10. Although pure ethanol is about 33% less energy dense compared to gasoline, alcohol burns more efficiently than gasoline in a typical EFI vehicle and the actual MPG loss will be significantly less. OPs ~7% loss going from E10 to E70 seems accurate.

During normal, closed loop operation of our cars, the ECU should be able to compensate for fairly high percentages of ethanol. However, during the warm up period and WOT conditions, when the car is open loop mode, it will use engine maps that have been tuned on whatever regular gas was when the car was made (for us, E10). So, if you try to run too high of an ethanol percentage, you may experience some trouble during cold starts or hesitation during hard acceleration. These problems can be fixed by going back to a lesser ethanol percentage or by changing the mapping in the ECU. In our case, since reprogramming or replacing our ECU is difficult, one could also add a piggyback ECU that can fool sensor values to the factory ECU and do its own mapping.

There's a lot of debate out right now about how high is too high for most of the non flex fuel vehicles out there. currently, the EPA has approved E15 for use in all cars 2001 and newer. IMO, up to about E25 shouldn't pose any issues in just about every car made since the late 90s. To get to E25, you'll want 4 parts E10 with 1 part E85. I think that would be a good blend for our cars and any time I fill up with E85 available I might do it.

About water...
Alcohol will mix with water, but gasoline won't. If you get all the water out of the alcohol, the alcohol and gasoline will mix. I've always heard that water in your gas tank can be detrimental to an engine, but evidently, if you can use straight alcohol as a fuel, up to about 20% of it can be water and it burns just fine. With a blend of ethanol and gasoline, if water is reintroduced, the mixture can separate and the bottom of the tank may contain an alcohol/water mix with the gasoline floating on top. As long as no water gets in your gas tank, this won't happen. If it does, you may get some cold start problems.

About corrosion...
Alcohol and water aren't really more corrosive than gasoline, but they do accelerate the corrosion of different type of materials than gasoline. This is one on my main concerns with prolonged use of higher alcohol content in the fuel. Now, cars since the 80s are made with components assuming the possibility of 10% ethanol in the fuel. Will a higher percentage wear out components faster? i see information in both directions. On one hand, the alcohol can actually keep components cleaner and they may last longer. On the other hand, rubber, plastic, and aluminum components could corrode faster. The details are kind of on a part by part basis and up for debate I guess.

TLDR:
If E85 is avaliable and cheap, add a gallon or two to your tank and don't worry about it.
 

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Thanks Johnny. Thats my general feeling and experience. One it gets down to 32 F and you do not use a block heater or go 3/4 or more throttle you wont get the fuel trim CEL.

The one part I heard that was not mentioned was that when e85 is burned the results makes the o2 sensor think the engine is running richer than it is and causes it to further lean out the afr where in fact it should enrich it.
 

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Thanks Johnny. Thats my general feeling and experience. One it gets down to 32 F and you do not use a block heater or go 3/4 or more throttle you wont get the fuel trim CEL.

The one part I heard that was not mentioned was that when e85 is burned the results makes the o2 sensor think the engine is running richer than it is and causes it to further lean out the afr where in fact it should enrich it.
This is not correct. In fact it will typically MAX out the fuel trims adding all the % fuel allowed for positive correction.

There's no benefit to a normally aspirated engine in using ethanol unless the engine suffers from knock/ping/detonation from poor octane availability for the market. It can be used to increase the octane by cutting it into the gasoline % used. No matter what the MPG will go down however, less any gains from restored full ignition timing no longer being retarded by the ECM by the knock sensor.
 
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