E85 Fuel Consumption

[dracy69]

So I just filled my Regal up today with E85.

I got called for jury duty so I have been in Riverhead and came across a gas station selling E85 for very cheap. 3.15 a gallon. That's more than a dollar cheaper per gallon than premium.

So needless to say I filled it up with E85.

Now for the important stuff, the fuel mileage. I got my car a week and a half ago. I used a tank and a half roughly, averaged 24mpg and covered a little over 600 miles. That all works out so it seems the fuel mileage indicator is accurate in the car thus far (no surprise there). This is a lot of mileage covered thanks to the new car syndrome. It was mixed highway, around town, and hooning about 😀. If I was to drive back and forth to work and not go everywhere with my friends at night my average would be more like 25-26 mpg and maybe 28 in the winterish months when I am in school (when I have no free time, and all highway). If I had a strictly highway trip (drive to North Carolina say) then this car can pull off 30-32 mpg at 65-70 mph. This is all on premium.

After filling up on E85, driving down Rt. 25 (50mph zone, 2-3 stoplights that were red) then getting lost in Riverhead trying to get back to the court (Main St. 20mph max stop and go) then taking the Expressway home then the back roads needed to get to my driveway, I'd say a 65/35 split between highway/city driving respectively. And my average was so far for today.

*drum roll*

23.1 mpg

I am very pleased thus far, but I should point out the car has been babied more so far on E85 than it was my first tank and a half on premium. I'll be sure to post what it ends up at by the end of the tank and I have some aggressive driving mixed in there but for now I'm going to predict 21-22mpg tank average. Hoping for a 2-3 mpg difference with similar driving. That is within the 5-10% loss GM calls for on this engine.

Using 18 gallons, at 24mpg, I get a 432 mile range, with 50 miles a day on average of driving that is a little over 8 days or roughly 3 and a half tanks a month. My fuel cost would be roughly 220 dollars with premium at 4.20 a gallon.

18 gallons at 22 mpg (guesstimate so far) would yield me a 396 mile range. just under 8 days which translates to just under 4 tanks of fuel. At 3.15 a gallon for e85 my cost would roughly be 220 dollars.

At an 8% drop it would pin the break even point at just under a dollar cheaper for E85 (premium was really 226 I think) which is surprising. I personally figured given my current circumstances E85 would be cheaper but it would seem I am breaking even. No complaints there and I guess paying into corn subsidies instead of oil subsidies isn't so terrible. I'll have to see if I notice a performance difference. If I do then I might be willing to take a small hit (10 dollars maybe) if E85 is only like 60-80 cents cheaper to get some more performance that month.

Any thoughts?

 

[daryll]

dracy -
This is something that I have lots of experience with. Since my first fill-up I have been running E85 in my T07, and now have 9,500 miles on the car. The overall fuel mileage according to the trip computer is 22.1 mpg. All of my other results are basically exactly as you have discovered. I don't have a point of comparison to running premium gas, as the only premium that I burned was in the tank when I picked up the car, and I drove it pretty easy the first 500 miles or so. Based on everything that I have read, our turbos should perform better on E85 than on premium - the computer is capable of holding boost up to 21 psi and the injectors are sized for fuel flow at that power. Pretty cool stuff in my opinion. To my knowledge, our turbos and new Bentley's are the only cars that actually optimize performance when running E85.

Financially, I have made the same exact calculations as you have - when there is close to a dollar difference between premium and E85 the overall cost per mile is a wash. If the difference is less, the E85 is more expensive. In my case, I run it anyway as I'm still getting roughly the same overall mileage that I got in my previous car (Pontiac G8 GT) and much lower fuel cost. We can talk for hours about the silliness of the ethanol subsidies that our government is putting out there, but my thinking is that since we have already brewed up the corn squeezings I might as well burn them. I'm in Ohio, and E85 is relatively easy to find. I have driven as far as Davenport Iowa and back, through Illinois and Iowa, and have always been able to find E85. Only one time did I have to through a couple gallons of premium into the tank to get me to the closest E85 station.

One other thought - I have no way of knowing if this is true or not - it seems like we are getting a little more than 220 HP out of the little engine when running on E85. I could be completely wrong, but as heavy as these cars are the performance from about 50 to 80 mph seems to be pretty strong - just my seat of the pants opinion. It does seem like it would be very easy to get even more power if you fully optimize for 100+ octane.
Enjoy your new car - so far I'm very happy with mine!
Daryll

 

[dracy69]

I haven't noticed much of a performance difference so far, I'll have to tool around at higher speeds I think this car's torque is limited at low speeds.

And it's the 270 lb-ft of torque that moves this car, not the 220hp.

I'll maybe beat on it a little tomorrow, right now the average for the tank is at 21.5, it'll go up to 22.1 probably by the time I make it to work tomorrow, maybe 22.5 by the time I make it home. So I can afford a little play time without killing my FE.

I noticed, IDK if I said this, that the car on the highway has gone relatively unchanged on E85. the Instantaneous will read 30-32 on level highway, 55-60 down hill, and 25-28 uphill. On premium it may be 2 mpg more all around but it's still pretty close. Where the car loses it's efficiency is in city driving. In a big way. That seems to be where I'm losing all of my fuel economy, the second this car get's into stop and go anything with E85.

So as an update, if you do all highway, E85 might actually benefit you, if you do over half highway but still a good amount of around town you can break even on E85, like I am thus far. If you do majority city driving, E85 will not be worth it. Once the turbo does anything it siphons alcohol like a frat house.

daryll, good to see you can back up my findings so far.

 

[GottWhat]

We drive about 95% city/suburban with our Turbo and our E85 fuel economy was less than 18 MPG but we stuck with E85 because it was a dollar less expensive than premium. Will have to see how it does with more freeway driving.

PS: Our 2011 Silverado 4x4 extended cab (5.3L V8) achieves 15 MPG in similar driving but only requires regular grade...

 

[daryll]

I haven't noticed much of a performance difference so far, I'll have to tool around at higher speeds I think this car's torque is limited at low speeds.

And it's the 270 lb-ft of torque that moves this car, not the 220hp.

I'll maybe beat on it a little tomorrow, right now the average for the tank is at 21.5, it'll go up to 22.1 probably by the time I make it to work tomorrow, maybe 22.5 by the time I make it home. So I can afford a little play time without killing my FE.

I noticed, IDK if I said this, that the car on the highway has gone relatively unchanged on E85. the Instantaneous will read 30-32 on level highway, 55-60 down hill, and 25-28 uphill. On premium it may be 2 mpg more all around but it's still pretty close. Where the car loses it's efficiency is in city driving. In a big way. That seems to be where I'm losing all of my fuel economy, the second this car get's into stop and go anything with E85.

So as an update, if you do all highway, E85 might actually benefit you, if you do over half highway but still a good amount of around town you can break even on E85, like I am thus far. If you do majority city driving, E85 will not be worth it. Once the turbo does anything it siphons alcohol like a frat house.

daryll, good to see you can back up my findings so far.

Yes, it looks like we have pretty much identical results. Agreed - torque makes it go, not HP. Still laughing about the frat house comment!!
D

 

[dracy69]

We drive about 95% city/suburban with our Turbo and our E85 fuel economy was less than 18 MPG but we stuck with E85 because it was a dollar less expensive than premium. Will have to see how it does with more freeway driving.

PS: Our 2011 Silverado 4x4 extended cab (5.3L V8) achieves 15 MPG in similar driving but only requires regular grade...

Run your Regal on Premium if you are doing all city driving, it will be cheaper.

 

[GottWhat]

Run your Regal on Premium if you are doing all city driving, it will be cheaper.

Good advice. I was only buying the E85 because it was $1 less per gallon but did fill up with premium the last fill up since the difference was only 80¢ and have already noticed an improvement in MPG.

Glad E85 is working out great for you though

 

[dracy69]

even at 1 dollar less per gallon premium will save you money.

E85 is something I can use but I'll probably still run premium most of the time. E85 is gaining some popularity around here on LI but not quite everywhere so it's not always available for me. I know of a station on my route to work, one near my job, and this one in Riverhead. That's it so far.

 

[DT-T03]

I filled up with E85 for the first time (6 fill-ups since new) and I think it'll be my last. E85 was only about $.60/gallon cheaper but I thought I would give it a shot just to see if the car responded differently. It did; the economy fell about 20% which makes it about a wash. Also, like stated earlier, the car seems to be much less efficient in "city" driving versus "highway". E85 is mildly available in my area SE Michigan/Detroit area but most of the stations seem to be within $.60/gallon of regular gas, so there's very little motivation to make the effort and go out of my way to get to the E85 stations.

FWIW the E85 didn't fix my Bluetooth problem ... 😛

 

[Stickman]

I will throw in my results too. They indicate an 11% loss in mileage on E85 for combined hwy/city driving. Much closer to gasoline mileage on the highway.

Keep in mind that According to the ASTM specs, E85 is more like 78% ethanol in most areas, to make the minimum vapor pressure.

Also from a prior thread, the turbo can produce a 20 inches Hg boost, not 20 p.s.i.. This is more like 9.8 p.s.i., which boosts the 9.3 compression ratio to an effective compression ration of 14.5:1, which is more ideal for E85.

Lastly, as an alternative to the cost efficiency of E85 vs. Premium, and assumming regular gasoline contains 10% ethanol and has a minimum octane of 87, mixing 3 parts regular gasoline with 1 part E85 produces a Premium grade octane at less than the cost of Regular.

Coincidentally, this is about a 30% ethanol blend, which is typically an ideal blend of ethanol for cost vs. milage in most FFVs.

 

[daryll]

Here is my update - my results do not match Stickman at all. At 11,000 miles I switched from E85 to premium, and my highway mileage went up from 23 average to 30 average, with one tank over 32 mpg. Based on this, E85 would have to be at least 30% less expensive than premium, and that would still not cover the hassle factor of extra fill-ups. now have close to 14,000 miles and will probably stick with premium for the rest of my time with this car. Still, the E85 was an interesting experiment for me. I'm hopeful that GM will bring the diesels in next year when my lease is up.
Daryll

 

[dracy69]

You made that jump from the same conditions? That is a lot worse than my results

 

[daryll]

Exactly the same conditions. I drive mostly highway and country two lane roads, usually put 35,000 miles per year on my cars. The first tank when I switched back to premium was just over 30 mpg (that tan was mostly highway) and have run premium since. The tank that I was referring to in my post was a fill-up near Trenton, NJ, then a drive to Syracuse, NY, then back towards Ohio. When I filled up again near my office I had driven 580 miles (32+ mpg). Best range that I ever did on a tank of E85 would have been about 450 miles. Much as I like the concept of running E85 the reality seems to indicate that that premium is much less expensive per mile and reduces my number of fueling stops by 25+%.

My seat of the pants opinion is that there is no performance difference either. It seems like E85 should have more power based on what I have read about the boost and injector sizing, but I really cannot tell the difference. May look into the performance tune...

Daryll