Bonus, E85 burns much cleaner, lower emissions, less carbon deposit, good for engine life.

Individual results will vary. You gotta do your own math. The crossover depends on the % price difference. But lower emissions, longer engine life, and increased hp are worth something too. I would run it if it were 20% cheaper.

 

I have done the math and it came out to half the mileage vs Arco 87. Which is why I'm very skeptical of any claim of it being better. I can not calculate mileage on someone else's car at a different elevation...

if e85 was half the price it would just be the same cost. But its only $1 cheaper and not worth it IMO.

 

E85 is $2.69/gal; 22 mpg

 

I highly doubt that. Have you reset the average mpg meter on a full tank fill up? I was getting closer to 14mpg average with e85.

 

I don't recall any claims that E85 is more or less economical MPG wise. Just ecosystem wise., with everything considered.

 

Your numbers are all over the place and your math is fuzzy. 260 is not half of 400.

In any event your results are nothing close to typical. I’ve never heard of anyone getting mileage that terrible on E85 in a flex fuel car, unless something was terribly wrong.

You can’t really pin down a precise number because gasoline chemistry varies so much, but gasolines energy content is only about 25% more than that of ethanol. But it doesn’t stop there, because ethanol burns more efficiently than gasoline in an IC engine. This is well known theoretically and well proved empirically. How much more efficiently depends on whether the engine is optimized for ethanol or for gasoline or somewhere in between.

An engine optimized for ethanol (not what HHR has) would come close gallon-for-gallon to one optimized for gasoline.

A bunch of things can contribute to the engine failing to produce a correct a/f ratio or efficient complete combustion. Bad O2 sensors, for one.

Get your engine fixed.

Some things you could try:

-With a capable scan tool, read the stored ethanol %, then sample the fuel and verify that they agree.

-With a scan tool, run the engine and monitor the a/f and fuel trims and verify that they are consistent with the actual ethanol %.

-Go back to E10 and see if the stellar mileage returns

 

Sorry to drag up an old thread, but it seemed better than creating a new one for basically the same topic.
There's a gas station that I regularly pass that I'm pretty sure has E85 for around $3/gal. Regular gas is around $5 - $5.50, so this seems like a big enough difference that I should consider it.
I have a 2011 LT. Anything important I need to know about using E85? Can I just mix it with regular gas, or should I try to get the tank as empty as possible before putting E85 in?

 

Those prices make E85 attractive. GM says you can mix E85, E10, and E0. If you have a 2.4 they recommend 91 octane minimum.

You will get somewhat lower mileage but the prices you mention will more than make up for it. There are additional benefits to E85. It burns cooler and cleaner and leaves the engine cleaner, potentially giving better engine life, and the car will have slightly more power in most cases. You may notice the heater takes longer to warm up the cabin.

Know that E85 is no longer 85% ethanol. The range is 51-83%. Because the cost of ethanol is normally cheaper than gasoline, producers have an incentive to maximize the ethanol in the blend, but they're supposed to reduce the ethanol content in Winter. This prevents hard starting in places where the weather gets cold.

Your car detects a "refueling event" and recalculates the % ethanol using data from its various sensors, so be sure if check engine light (CEL, or Malfunction Indicator Light, "MIL" in GM speak) is on to address it. I would not change to or from E85 while there is a problem with the emission system that would set a CEL. There is no ethanol sensor, per se. Be sure to shut the car off when refueling.

 

And, ALWAYS refuel with the engine off. That is how it knows to recalculate.