Experimenting with E85

[A_Harman]

Road trip last weekend to western New York to see the progressive rock band YYNOT in Horseheads. (No that is not code!)
Lovely weather and vibrant fall colors along I-86. Had some extra time, so made side trips to the Glenn Curtiss Museum in Hammondsport, and Watkins Glen Raceway.
Mild, sunny days and cool, crisp nights. Yeah, I like autumn.

October 14 fill-up.
6.6 gal E85 @ $3.55
6.6 gal 87 @ $3.85
Weighted cost per gallon = $3.77
Residual in tank was 50% E85. (2.4 gallons)
Total E85 in tank: 7.8 gal
Proportion E85=50%
Fuel economy of previous fill (50%) was 370 miles/13.2 gal = 28.0 mpg
Adjusted Cost per mile = 15.2 cents

October 15 fill-up.
0 gal E85, just couldn't find it anywhere in western NY.
5.8 gal 93 @ $4.60
5.8 gal 89 @ $4.20 Respecting my car's 91 minimum octane requirement while remaining a cheapskate.
Weighted cost per gallon = $4.24
Residual in tank was 50% E85. (4.0 gallons)
Total E85 in tank: 2.0 gal
Proportion E85=13%
Fuel economy of previous fill (50%) was 339.5 miles/11.6 gal = 29.3 mpg
Adjusted Cost per mile = 15.7 cents

October 16 fill-up.
6.2 gal E85 @ $2.97 Great find in Ashtabula County, Ohio!
5.8 gal 87 @ $3.57
Weighted cost per gallon = $3.49
Residual in tank was 13% E85. (.47 gallons)
Total E85 in tank: 6.7 gal
Proportion E85=43%
Fuel economy of previous fill (13%) was 357.4 miles/12.0 gal = 29.8 mpg
Adjusted Cost per mile = 13.2 cents

October 17 fill-up.
6.0 gal E85 @ $3.46
6.3 gal 87 @ $3.96
Weighted cost per gallon = $3.67
Residual in tank was 43% E85. (1.4 gallons)
Total E85 in tank: 7.4 gal
Proportion E85=47%
Fuel economy of previous fill (43%) was 346 miles/12.3 gal = 28.1 mpg
Adjusted Cost per mile = 14.6 cents

Back to the commuting daily grind in Detroit now.

 

[A_Harman]

Well I had a lot of fun on my long distance trip and here is the info to go with it from my truck. Had to fill up twice on the road, each time with 91 premium with 0% ethanol, didn't have any E85 stations that I was able to stop at during the trip. Of course I managed to forget my tuning laptop when I left so I don't have the alcohol sensor info for the trip so I'm going strictly on calculations for the ethanol content.

I had filled up with E85 the week before the trip, had about 40 miles of local driving before the start of the trip on Friday. Went 286 miles before I had to fill up the first time, almost all interstate at around 70 MPH the whole way. I used 22.882 gallons of E85 for a calculation of 12.5 MPG. It cost me $101.73 for the E0 premium at $4.649 per gallon. The alcohol content calculates to 2.36 gallons left in the tank which is about 9.1% alcohol content in the tank after fill up, so around what you expect for premium gas with 10% ethanol content.

Barely had any local driving at my destination, under 10 miles total, everything else was highway and interstate driving. Heading back on Sunday I went 427.4 miles before stopping to fill up a little more than half way home, mostly 60-70 MPH depending on the road I was on. I used 22.909 gallons of premium for a calculation of 18.7 MPG. It cost me $105.35 to fill up again with 91 premium at $4.599 a gallon. The alcohol content calculates to .281 gallons left in the tank which is about 1.1% alcohol content in the tank after fillup, so almost no alcohol left in the tank at all.

I ended up at almost half a tank when I got home at around 230 miles, so if that is 13 gallons used it would be around 17.7 MPG. This is only an estimate of course as I don't know the exact amount of fuel used. Still the difference of 12.5 MPG to 18.7 MPG is about a 33% difference between E85 and premium fuel, which is just about the difference I paid for the local E85 vs the road premium. So it would be a wash as far as cost is concerned here. If E85 would have been available I may have also had to add an extra stop for fuel in before reaching home, so if you are looking at the distance and time premium may just be the better choice (not that I didn't stop multiple times on my 7+ hour trip, neither my back nor my bladder wants to be stuck without a break for that long anymore).

Its also interesting that the E85 ends up going to 33% drop in fuel economy vs premium when driving on the highway. I know my truck isn't exactly fuel efficient at higher speeds since its a giant brick when it comes to aero but the city driving only suffers around 20% loss. I would be curious to see how a 50% blend would work out since that gave me the best fuel economy for the overall cost. Not planning on any future long distance trips anytime soon but perhaps the next time I'll take a couple of E85 filled gas cans with me to make my own 50% blend as well as start out with that before leaving home on the trip.

That's a gut-wrenching decrease in fuel economy on straight E85. I can see why most people try E85 once, and not again.
What was the E85 cost on your fillup before the trip? I'm hoping that at least the cents per mile was the same as E0 Premium.

 

[LDM]

That's a gut-wrenching decrease in fuel economy on straight E85. I can see why most people try E85 once, and not again.
What was the E85 cost on your fillup before the trip? I'm hoping that at least the cents per mile was the same as E0 Premium.

Fill up cost was $78.91 vs $119.91 that would have been cost of premium, so $41 less for E85 at 35% the cost of premium. Pretty much a wash as far as cost was concerned, since it was a 33% drop in fuel economy vs the 35% reduced cost of E85 against premium. A 33% loss is a lot more than I originally expected considering its only around 20% for local driving. If I wasn't tracking the overall costs, I definitely agree that most people would see the huge decrease in mileage and not want to bother using it again. Even more so if you can't get it for 30-40% less than the cost of the gasoline that would normally be used. Since I have to run premium in my truck it still makes sense but if I had a 5.3 instead of the 6.2, 87 octane would be the best choice for cost purposes.

I would like to see what around 50% alcohol content would do on long distance trips but I suppose I'll need to plan another one before I can see how my truck does. Maybe I won't forget my tuning laptop next time either so I can get some proper data logs in as well.

 

[A_Harman]

October 20 fill-up.
6.8 gal E85 @ $3.85
6.9 gal 87 @ $4.35
Weighted cost per gallon = $4.05
Residual in tank was 47% E85. (.9 gallons)
Total E85 in tank: 7.7 gal
Proportion E85=46%
Fuel economy of previous fill (47%) was 362.4 miles/13.7 gal = 26.5 mpg
Adjusted Cost per mile = 15.5 cents

 

[LDM]

That's a gut-wrenching decrease in fuel economy on straight E85. I can see why most people try E85 once, and not again.
What was the E85 cost on your fillup before the trip? I'm hoping that at least the cents per mile was the same as E0 Premium.

One other question I just thought of was does your engine gain any HP/TQ when using E85? I know the 4.3 V6 and 5.3 V8 both get increased power ratings when using E85 on the flex fuel vehicles. I've noticed a similar increase when data logging with HP tuners on my truck, which makes sense as the engines are all from the same family. Not sure if the small turbo engines would also gain power as well or if you end up with better fuel economy instead of more power.

I'm looking into making some changes in my tune to try to improve both power and fuel economy, although I probably won't mess with that too much during the winter. Don't need something happening when its too cold out with my truck. I'll probably wait until spring before I upload any tunes and get some more data logging so I have more information to apply to the tuning.

 

[A_Harman]

Catching up on fuel fill data in normal commuting service:

October 26 fill-up.
6.6 gal E85 @ $3.36
7.4 gal 87 @ $3.86
Weighted cost per gallon = $3.67
Residual in tank was 49% E85. (.7 gallons)
Total E85 in tank: 7.4 gal
Proportion E85=47%
Fuel economy of previous fill (46%) was 370.9 miles/14.0 gal = 26.5 mpg
Adjusted Cost per mile = 15.6 cents

October 28 fill-up.
7.0 gal E85 @ $3.60
6.2 gal 87 @ $4.10
Weighted cost per gallon = $3.81
Residual in tank was 47% E85. (1.1 gallons)
Total E85 in tank: 8.1 gal
Proportion E85=52%
Fuel economy of previous fill (47%) was 351.4 miles/13.2 gal = 26.6 mpg
Adjusted Cost per mile = 15.6 cents

November 2 fill-up.
6.4 gal E85 @ $3.49
6.2 gal 87 @ $3.99
Weighted cost per gallon = $3.75
Residual in tank was 52% E85. (1.56 gallons)
Total E85 in tank: 8.0 gal
Proportion E85=51%
Fuel economy of previous fill (52%) was 337.4 miles/12.6 gal = 26.8 mpg
Adjusted Cost per mile = 15.3 cents

November 4 fill-up.
6.3 gal E85 @ $3.68
6.5 gal 87 @ $4.18
Weighted cost per gallon = $3.90
Residual in tank was 51% E85. (1.43 gallons)
Total E85 in tank: 7.7 gal
Proportion E85=50%
Fuel economy of previous fill (51%) was 338.7 miles/12.8 gal = 26.5 mpg
Adjusted Cost per mile = 15.6 cents

November 8 fill-up.
6.5 gal E85 @ $3.80
6.3 gal 87 @ $4.30
Weighted cost per gallon = $4.02
Residual in tank was 50% E85. (1.4 gallons)
Total E85 in tank: 7.9 gal
Proportion E85=50%
Fuel economy of previous fill (50%) was 350.3 miles/12.8 gal = 27.4 mpg
Adjusted Cost per mile = 15.6 cents

Keeping close to 50% E85.

 

[A_Harman]

Latest updated fuel economy graph:

The linear and polynomial curve fits are now almost the same. The linear curve fit actually predicts fuel economy at 0% E85 better than the polynomial.

 

[A_Harman]

Latest fuel cost per mile graph:

Actual and adjusted costs per mile bottom out at about 53%.

 

[LDM]

Filled up again a couple days ago, this time I did 12 gallons of 87 regular and 12 gallons of E85. Of course I forgot my tester when I went so I only know the alcohol % by my datalog, which is 40.4%. Alcohol content may be a little lower now that the colder temps have arrived here. I filled up for 23.992 gallons for a total of $74.63, premium would have been $97.86 so a savings of $23.23 before fuel economy is taken into consideration. I went 362 miles on the previous E0 premium, so right at 15 MPG overall. So far no issues with starting or running using E85 in the freezing weather we have had around here since last week.

 

[jetman]

@swathdiver and myself have done some experimenting with E85 and mixes. We both have a GM suv with 6.2L premium recommended vehicles.

Here's some data @swathdiver has put together over the years:

Over the last 4 yrs and 40k miles I have run regular unleaded, mid-grade, premium, and up to a 20% mix of E85 & premium. Mine runs fine on all 4 fuels. I drive my vehicles conservatively. Gas mileage suffers on mid-grade and regular. Gas mileage doesn't suffer on the 20% mix. Cost per mile goes down because where I buy E85 it cost $1 per gallon less than premium. So, When I fill-up my 25 gal tank the 5 gals of E85 I put in saves me $5/fill-up, or $0.50/gal. Where I live premium is $3.50/gal and E85 is $2.50/gal.

On premium or 20% E85 I get 16+ mpg locally. On premium only on long hwy trips I get 19 mpg averaging 65 mph. I'm never able to find E85 when on a long hwy trip.

My vehicle is a 2007 Yukon Denali with all-aluminum L92 6.2L w/182k miles, It is NOT a flex fuel vehicle. GM recommends premium but it does great on a 20% mix too. My 6.2L doesn't have DOD/AFM. It does have VVT.

 

[LDM]

@swathdiver and myself have done some experimenting with E85 and mixes. We both have a GM suv with 6.2L premium recommended vehicles.

Here's some data @swathdiver has put together over the years:
View attachment 127192

Over the last 4 yrs and 40k miles I have run regular unleaded, mid-grade, premium, and up to a 20% mix of E85 & premium. Mine runs fine on all 4 fuels. I drive my vehicles conservatively. Gas mileage suffers on mid-grade and regular. Gas mileage doesn't suffer on the 20% mix. Cost per mile goes down because where I buy E85 it cost $1 per gallon less than premium. So, When I fill-up my 25 gal tank the 5 gals of E85 I put in saves me $5/fill-up, or $0.50/gal. Where I live premium is $3.50/gal and E85 is $2.50/gal.

On premium or 20% E85 I get 16+ mpg locally. On premium only on long hwy trips I get 19 mpg averaging 65 mph. I'm never able to find E85 when on a long hwy trip.

My vehicle is a 2007 Yukon Denali with all-aluminum L92 6.2L w/182k miles, It is NOT a flex fuel vehicle. GM recommends premium but it does great on a 20% mix too. My 6.2L doesn't have DOD/AFM. It does have VVT.

Good data as well. Curious as to how your vehicles would perform if the alcohol sensor was added and the flex fuel tables and options were added in your tune. I never tried to run E85 before converting my truck but the virtual flex fuel option was enabled when I starting doing the tuning changes.

 

[jetman]

I've also tried the 4 various fuels in my 2007 Toyata Fj Cruiser premium recommended 4.0L 1GR-FE w/VVT. Gas mileage doesn't change no matter the fuel, so I have run regular in it since 2009, 200+k miles ago. Engine always runs good. I always drive conservatively. It's never thrown a code.

 

[LDM]

Filled up again today, 11.138 gallons E85 at $2.229 for $24.83 and 11.634 gallons 87 octane at $3.199 for $37.22, total of $62.05 for 22.772 gallons. My MPVI2 has decided to stop working for some reason so no data log info on the alcohol content but I at least remembered my tester this time, it was about 70% for the E85 so the winter blend is a bit lower on alcohol content overall. Mileage ended up at 11.2 MPG, which is pretty good and not much different that what I would get on premium during the colder months. 255.4 miles since the last fill up, the truck mileage calculator was at 12.6 MPG, so it was off by around 1.4 MPG this time. Calculated alcohol content would be 3.228 gallons remaining at 40.4% (1.3), 11.634 87 octane at 10% (1.16), and 11.138 E85 at 70% (7.8), for a total of 39.5% alcohol content (10.26). Premium would have been $3.879 for $88.33, which is a savings of $26.28 before mileage is considered.

 

[A_Harman]

Filled up again today, 11.138 gallons E85 at $2.229 for $24.83 and 11.634 gallons 87 octane at $3.199 for $37.22, total of $62.05 for 22.772 gallons. My MPVI2 has decided to stop working for some reason so no data log info on the alcohol content but I at least remembered my tester this time, it was about 70% for the E85 so the winter blend is a bit lower on alcohol content overall. Mileage ended up at 11.2 MPG, which is pretty good and not much different that what I would get on premium during the colder months. 255.4 miles since the last fill up, the truck mileage calculator was at 12.6 MPG, so it was off by around 1.4 MPG this time. Calculated alcohol content would be 3.228 gallons remaining at 40.4% (1.3), 11.634 87 octane at 10% (1.16), and 11.138 E85 at 70% (7.8), for a total of 39.5% alcohol content (10.26). Premium would have been $3.879 for $88.33, which is a savings of $26.28 before mileage is considered.

You have a good situation for E85 pricing at almost a full dollar per gallon less than regular.
I normally get E85 at 50 cents per gallon less than 87. Getting it at a dollar less is rare for me. Although yesterday I filled up at a station that was $2.17 E85, $3.17 87.
Getting E85 at a lower price ratio to 87 is a good way to save money:

My Buick data shows if the E85 price is higher than 87.5% of 87, fuel cost per mile isn't necessarily below average.

 

[A_Harman]

Here is the tank fill data for the last month:

I have been staying at 50% E85 fillups. Fuel economy has been in the range of 25.4 to 27.8 mpg.
Summary data for the 72 tank fills is in the first 3 rows. Overall I have saved $325 over 24,000 miles of driving by running E85 blends. That's about 8%.

 

[LDM]

You have a good situation for E85 pricing at almost a full dollar per gallon less than regular.
I normally get E85 at 50 cents per gallon less than 87. Getting it at a dollar less is rare for me. Although yesterday I filled up at a station that was $2.17 E85, $3.17 87.
Getting E85 at a lower price ratio to 87 is a good way to save money:
View attachment 130261
My Buick data shows if the E85 price is higher than 87.5% of 87, fuel cost per mile isn't necessarily below average.

Yeah, IL does have a lot of corn and ethanol plants, there is one right in the town I live in, although we have no E85 at any of our pumps for some reason. Have to travel about 5 miles to a little town that has a Casey's with E85 and E15 pumps to get it but so far it seems to be worth it. Premium just keeps going up in price around here in comparison to 87 octane, its at least 50-60 cents more every time I check the prices. Even if I was running straight E85 in my truck it would still be worth it as the spread from premium is now above 40%.

 

[A_Harman]

December 14 fill-up.
6.9 gal E85 @ $3.16
6.5 gal 87 @ $4.16
Weighted cost per gallon = $2.88
Residual in tank was 50% E85. (1.1 gallons)
Total E85 in tank: 8.0 gal
Proportion E85=51%
Fuel economy of previous fill (50%) was 360.1 miles/13.4 gal = 26.9 mpg
Adjusted Cost per mile = 10.8 cents

December 16 fill-up.
13.25 gal 89 @ $3.33
Weighted cost per gallon = $3.26
Residual in tank was 51% E85. (1.2 gallons)
Total E85 in tank: 1.2 gal
Proportion E85=8%
Fuel economy of previous fill (51%) was 328.7 miles/13.25 gal = 24.8 mpg
Adjusted Cost per mile = 15.3 cents

Decided to do a series of tank fills on 89 octane, probably 6 of them.

 

[LDM]

Filled up again yesterday, both because of the storm that was coming today and I was down to my last couple gallons of fuel. I did 12 gallons of 87 octane at $2.549 for $30.59 and 11.310 gallons of E85 at $1.919 for $21.70. Total of 23.130 gallons for $52.29, premium would have been $3.569 per gallon for total of $83.19, which results in a savings of $30.90 before mileage considerations. That ends up being a 37% cost difference for my mix and would be a 46% cost difference if I had just filled up with E85. Ended up getting 286.6 miles before filling up, 14 MPG on the GM display vs 12.3 MPG calculated, so off by about 1.7 MPG this time for the lie o meter in the truck. I did get a new data logger that allowed me to see that my alcohol content was 42.4%, which when I tested the E85 with my tester it was 75% ethanol. So calculated it would be 2.87 gallons remaining (at 39.5%, 1.13), 12 gallons 87 octane (1.2), and 11.310 gallons E85 at 75% (8.48), for 10.81 gallons of alcohol at 41.6%, so within .8% of the alcohol sensor.

12.3 MPG is not really much different than the mileage I see on premium during the winter, especially with some remote starts to warm up the truck before driving it. I may end up filling up with just E85 for a the next few fillups as the cost difference is almost 50% vs premium at this point and to see how well it does during the cold winter months.

 

[A_Harman]

The E85 pumps in Michigan have a sign on them saying the ethanol content can vary from 51 to 83%. It would be nice to be able to buy 51% ethanol fuel right out of the E85 pump so I wouldn't have to run two transactions at the pump. That's a bummer standing out in the wind and cold of a Michigan winter. But since the actual ethanol content isn't posted on the pump, I can't know what I'm actually putting in my tank.

Your new data logger seems to read correct ethanol content. What model is it?
So far I've been too cheap to buy a Scangauge, but I may have to go for it if I want to know my actual ethanol content.

 

[LDM]

The E85 pumps in Michigan have a sign on them saying the ethanol content can vary from 51 to 83%. It would be nice to be able to buy 51% ethanol fuel right out of the E85 pump so I wouldn't have to run two transactions at the pump. That's a bummer standing out in the wind and cold of a Michigan winter. But since the actual ethanol content isn't posted on the pump, I can't know what I'm actually putting in my tank.

Your new data logger seems to read correct ethanol content. What model is it?
So far I've been too cheap to buy a Scangauge, but I may have to go for it if I want to know my actual ethanol content.

I found an old MPVI original on Ebay for $100, so its the same HP tuners software. Really didn't find much else that had the full GM functionality for data logging that I wanted. Definitely agree with the standing in the cold right now, it sure would be nice to be able to dial in exactly the amount of ethanol I want in the fuel instead of having to make multiple transactions.