As luck would have it, there is actually an E85 station about 8 miles from my house. This is actually quite odd as I live outside the city, but I saw it as generally good news since I own a turbocharged car. OK, so I'm familiar with E85 (considerably higher octane but lower energy content per gallon) but am also clear that none of my vehicles are certified to run on it from a fuel system point-of-view.

My question is, assuming it would have any considerable benefit (to my reflashed 996TT), would it be safe and worthwhile to add a couple gallons of E85 to a tank of 92 octane standard dino gas? The hoped for result would be to create a tankful of 93-94 octane fuel.

I recognize this is probably a stupid question, but rest assured that my default mode would be NOT to do this. I've also never seen this question asked before so am just randomly curious. I just want to understand the following points.

1. Is it even safe to mix E85 with E10 (our normal fuel has 10% ethanol blend here)?
2. Assuming it's safe to mix, would it be reasonably safe to run through my stock fuel system on a limited basis?
3. Assuming it's safe to run this small amount of E85, would my reflashed ECU even benefit from it?

Again, be certain I wouldn't even attempt this without better understanding the ramifications of doing so, but due to the low price of E85 and the high octane rating, I am just curious if this could theoretically work to create a slightly higher octane blend of poor man's pump 93 or 94 (neither of which is available in my state). Thanks all.

 

Doing a bit of my own research, I did find this link:

http://en.wikipedia.org/wiki/E85_in_standard_engines

A highlight which might have relevance to my question:

Turbocharged engines

E85 gives particularly good results in turbocharged cars due to its high octane. It allows the ECU to run more favorable ignition timing and leaner fuel mixtures than are possible on normal premium gasoline. Users who have experimented with converting OBDII (i.e., On-Board Diagnostic System 2, that is for 1996 model year and later) turbocharged cars to run on E85 have had very good results. Experiments indicate that most OBDII-specification turbocharged cars can run up to approximately 39% E85 (33% ethanol) with no MILs or other problems. (In contrast, most OBDII specification fuel-injected non-turbocharged cars and light trucks are more forgiving and can usually operate well with in excess of 50% E85 (42% ethanol) prior to having MILs occur.) Fuel system compatibility issues have not been reported for any OBDII cars or light trucks running on high ethanol mixes of E85 and gasoline for periods of time exceeding two years. (This is likely to be the outcome justifiably expected of the normal conservative automotive engineer's predisposition not to design a fuel system merely resistant to ethanol in E10, or 10% percentages, but instead to select materials for the fuel system that are nearly impervious to ethanol.)
Fuel economy does not drop as much as might be expected in turbocharged engines based on the specific energy content of E85 compared to gasoline, in contrast to the previously-reported reduction of 23.7% reduction in a 60:40 blend of gasoline to E85 for one non-turbocharged, fuel-injected, non-FFV. The reason for this non-intuitive difference is that the turbocharged engine seems especially well-suited for operation on E85, for it in effect has a variable compression ratio capability, which is exactly what is needed to accommodate varying ethanol and gasoline ratios that occur in practice in an FFV. At light load cruise, the turbocharged engine operates as a low compression engine. Under high load and high manifold boost pressures, such as accelerating to pass or merge onto a highway, it makes full use of the higher octane of E85. It appears that due to the better ignition timing and better engine performance on a fuel of 100 octane, the driver spends less time at high throttle openings, and can cruise in a higher gear and at lower throttle openings than is possible on 100% premium gasoline. In daily commute driving, mostly highway, 100% E85 in a turbocharged car can hit fuel mileages of over 90% of the normal gasoline fuel economy. Tests indicate approximately a 5%-20%increase in engine performance is possible by switching to E85 fuel in high performance cars.

 

A simple answer would be no. Reason is the car's ECU can not correct for the amount of fuel it needs to run E85 now it can correct 25% up or down but that is still not enough to work with E85.

 

You're going to have to add more than just "a couple of gallons" to get 94 octane as E85 is rated from 94-96. You would need blend a 50:50 mix of E85 with 92 octane to get 94. Not worth it imo. You're better off blending race fuel or 100 octane pump.

 

I would caution anybody mixing E85 or any Ethanol blend with a gasoline tune. Mixing E85 is NOT the same as mixing some high octane gasoline to arrive at a little bit more safety. The reason is because Ethanol (or any non gasoline substitute) has a different stoichiometric ratio than gasoline. In the case of alcohol, you need MORE fuel per unit of air to achieve the same a/f ratio. So by mixing in alcohol into your gasoline, you actually will lean out the A/F ratio. Can your ECU compensate for this? That's the real question. But not wise to do without monitoring it. You can argue small amounts won't be harmful because while the A/F would get leaner, the octane would go up hence tolerating a leaner burn, but its taking a risk without A/F monitoring.

On the other hand, mixing in some racegas will raise the octane without drastically changing the A/F ratio (there are SMALL differences based on the SG of the paritcular fuel, but in general its very small).

 

I'm under the impression that E85 has octane rating of approximately 105. You can see that here: http://www.e85fuel.com/e85101/faqs/ethanol.php

Unless they are calculating it differently, but I've read that it varies from 98-106. It's supposed to have considerably higher octane than any other pump gasoline (short of pumping 100+ octane at a pump obviously).

 

So, the literature I've read says to keep the mix below 38% when using E85 in a non FF vehicle. The only remaining issue is whether or not the ECU could compensate for it, and I have at least one tuner telling me that it could not...which is certainly grounds for not wanting to pursue E85 except for the fact that it's actually cheaper than 92 octane in my area. So, hassle factor aside...it seems to be reasonably safe but probably wouldn't result in any increased performance at all in the application I'm suggesting. I still find this an interesting discovery nonetheless.

 

Talking to TTdude: I did a bit more research and believe that you were actually correct in your comparative rating of 94-96 (when compared to regular gasoline):

http://en.wikipedia.org/wiki/E85#Com...gular_gasoline

Looks like 94-96 is right. If that is the case, this whole thing is pointless as I thought it was considerably more.

 

The advantage of E85 isn't just the octane rating. It's how much "cooler" it burns. A good e85 tune will make considerably more power than a good MS 109 tune.

 

I wasn't planning to get tuned for it though, but great point you brought up. Thanks.

 

I am contemplating on an E85 conversion, I wish more gas stations around here had E85 though...