Sponsored

E85 gas mileage?

AZ18yote

Well-Known Member
Joined
Nov 24, 2017
Threads
11
Messages
3,220
Reaction score
1,523
Location
Arizona
First Name
Bryan
Vehicle(s)
2018 Mustang GT Prem PP Magnetic
There's a station off of Broadway and Val Vista that is routinely testing in the 80+% range. I use to splash blend my previous car and I tested every fill up. If it's in the area for you, I'd highly recommend it.
Wow really? That's the highest I've heard of in the valley? What station is that? I have been doing the Chevron at 48th st and Broadway it is pretty consistent. Avoid the Texaco at 7th st and Indian school like the plague it's the only place I consistently log knock.
Sponsored

 

T.Man

Member
Joined
Sep 23, 2018
Threads
3
Messages
19
Reaction score
11
Location
Mesa, AZ
First Name
Tyler
Vehicle(s)
2018 A10 GT
Wow really? That's the highest I've heard of in the valley? What station is that? I have been doing the Chevron at 48th st and Broadway it is pretty consistent. Avoid the Texaco at 7th st and Indian school like the plague it's the only place I consistently log knock.
It's a Chevron. It's right across the way from Home Depot. I'm on the East side, so I wouldn't use any other station, if I can help it :)
 

bootlegger

Enginerd
Joined
Jul 12, 2017
Threads
9
Messages
1,765
Reaction score
593
Location
Mount Pleasant, SC
First Name
James
Vehicle(s)
Ex 2008 Mustang GT Owner
2018 with PBD tune. On 93, I average around 18-20 mpg. With E85, I am down to 14-16 mpg. E85 is like $2.45 per gallon, and 93 is close to $3.50 per gallon.
 

Dusten

Well-Known Member
Joined
Jul 25, 2018
Threads
14
Messages
827
Reaction score
589
Location
Conway, Wa
First Name
Dusten
Vehicle(s)
2018 Ford Mustang, 2001 Ford Lightning, 1968 Ford Mustang
Man that is crazy I never seen e-85 that high in price it is usually around 2 bucks a gallon in Detroit area. Also most e-85 pumps say 51%-83% due to colder months they lower the ethanol percentage so I have seen it at 70% here and highest I've seen it is like 87%
Ya Seattle blows
 

Myshelby3425

Well-Known Member
Joined
Aug 27, 2015
Threads
77
Messages
2,170
Reaction score
554
Location
Miami
Vehicle(s)
2018 GT
2018 with PBD tune. On 93, I average around 18-20 mpg. With E85, I am down to 14-16 mpg. E85 is like $2.45 per gallon, and 93 is close to $3.50 per gallon.
Is that mostly highway miles? In city I do about 16-17 on 93 and on E85 10-12. E85 on the highway is still terrible, barely get anything better. I have a Lund tune
 

Sponsored

bootlegger

Enginerd
Joined
Jul 12, 2017
Threads
9
Messages
1,765
Reaction score
593
Location
Mount Pleasant, SC
First Name
James
Vehicle(s)
Ex 2008 Mustang GT Owner
Is that mostly highway miles? In city I do about 16-17 on 93 and on E85 10-12. E85 on the highway is still terrible, barely get anything better. I have a Lund tune
50/50 city and hwy. However, when I am not on the highway, I am usually on it pretty hard.
 

scottycameron

Well-Known Member
Joined
Jul 19, 2018
Threads
8
Messages
157
Reaction score
160
Location
North Central IL
Vehicle(s)
2018 GTPP1 Orange Fury
~13mpg on E85R Lund tune.

93 here is $3.90 per gallon E85 is $2.11.

I filled up on 93 the other day and about had a heart attack...I like the $28 fill ups better.
 

Rosni44

Member
Joined
Apr 25, 2020
Threads
1
Messages
5
Reaction score
0
Location
Houston
First Name
Oscar
Vehicle(s)
2018 5.0 PP1
I just got my Lund E85r tune on a 2018 5.0. My fuel range has been dropping when I pump gas. Every time I have filled up the tank I’m about 60 miles to empty. I have pumped gas at different stations and I have seen a decrease on my range at full. I let it fill up and my ranges have gone from 202, 187, and yesterday at full I was 176 to empty. I’m new to this so any input will help.
 

AZ18yote

Well-Known Member
Joined
Nov 24, 2017
Threads
11
Messages
3,220
Reaction score
1,523
Location
Arizona
First Name
Bryan
Vehicle(s)
2018 Mustang GT Prem PP Magnetic
I just got my Lund E85r tune on a 2018 5.0. My fuel range has been dropping when I pump gas. Every time I have filled up the tank I’m about 60 miles to empty. I have pumped gas at different stations and I have seen a decrease on my range at full. I let it fill up and my ranges have gone from 202, 187, and yesterday at full I was 176 to empty. I’m new to this so any input will help.
This is normal. Can depend on content etc. I bet if you do a KAM reset the first couple fill ups would be higher again but soon after you'll see the same decrease.
 

Sponsored

Bmaughan

Well-Known Member
Joined
Sep 26, 2019
Threads
70
Messages
473
Reaction score
63
Location
Az
First Name
Ben
Vehicle(s)
2015 procharged mustang gt
I’m supercharged but I’m getting only about 8mpg, 9 at best haha...

I should add my fuel is consistently about e90
 

WildHorse

N/A or GO HOME
Joined
Jun 28, 2017
Threads
216
Messages
8,466
Reaction score
6,534
Location
Home World: CLASSIFIED
First Name
ⓇⒾⒸⓀⓎ ⓈⓅⒶⓃⒾⓈⒽ
Vehicle(s)
'17 S550
Vehicle Showcase
1
Mileage will be directly proportional to the change in stoichiometric mixture, which is a better way to figure out how your current mileage will change. By definition gasoline is said to have a 14.64:1 air to fuel ratio. Ethanol on the other hand is said to have a 9:1 air to fuel ratio. To give you some background:

These are the ratios at which all the fuel should be burned, often refereed to as "stoich". If you have more fuel you're rich and if you have more air you're lean. Air fuel ratios are clearly fuel mixture dependent and in reality fuel mixtures like gasoline are a slew of chemicals and additives; The result is that actual stoich points are varied. No one is running perfect 14.64 gasoline or perfect 9.0 ethanol on the street. Outside of race or lab quality fuels where you are told the stoich point on the label, you don't know what your fuel's actual stoich point is. Furthermore these values are based on mass rather than volume so it would be much more difficult to calculate without knowing the chemical composition of the mixture. If we knew the exact composition it would be fairly easy based on molar mass.

To deal with this your car's oxygen sensors are used to check the gases coming out of your headers against the atmosphere and produce "lambda" equivalence ratio values, where 1.0 is stoich and anything less is rich and anything more is lean. This way the sensor/computer doesn't care what fuel you run, it can tell if you're rich or lean no matter what the stoich point of your fuel is. Your aftermarket AFR gauges or built-in AFR gauge in the car can multiply oxygen sensor lambda values by what they think your fuel's stoich point is. This is where you get errors on gauges because of fuel changes, gauge assumes you run gasoline and multiplies any lambda value from the oxygen sensor by 14.64. So if you pour in E85 your AFR gauge will be way off unless it's re-calibrated to know the stoich point changed. This is why I like seeing lambda values on my gauges more so than AFR values, more accurate for the purpose of telling lean/rich.

So if we know that stoich points of fuels are varied and cars use lambda values from oxygen sensors to deal with this. What can we do to calculate mileage accurately? The easiest way is to make some assumptions:

Most gasoline has ethanol in it, marine and a few other applications won't, but most of what you get from the pump is somewhere between gasoline and E10. We can use some basic math to see the following:

Pure Gasoline: 14.64 AFR * 1.0 = 14.64 AFR
Pure Gasoline and %10 Ethanol (E10): 14.64 AFR * 0.9 + 9 AFR * 0.1 = 14.08 AFR

So lets take the average of the two and assume most street gasoline is somewhere around 14.36 AFR to be safe since we know it has some ethanol in it, up to 10%.

Now let's look at E85:

Pure Gasoline and %85 Ethanol (E85): 14.64 AFR * 0.15 + 9 AFR * 0.85 = 9.85 AFR

So how much more fuel do you have in E85 vs street gasoline? We now know that for every 14.36 grams of air we need one gram of street gas and for every 9.85 grams of air we need one gram of e85. Like this:

100g air / 14.36 AFR = 6.96g of street fuel
100g air / 9.85 AFR = 10.15g of e85 fuel

What's the percentage increase of fuel delivery for our same 100g of air?

(10.15g - 6.96g) / 6.96g * 100 = 45.8%

So we see our fuel delivery will grow by 45.8%, this is of course by mass.

Now by volume @ STP:

Street Gasoline = 755 g/L
Ethanol = 789 g/L
E85 = (755g * 0.15 + 789g * 0.85) = 784 g/L

Liters of street gasoline per 100g of air: 6.96g / 755 = 0.0092 liters
Liters of E85 per 100g of air: 10.15g / 784 = 0.0129 liters

Percent change = (0.0129 - 0.0092) / 0.0092 * 100 = 40.2%

Now of course densities change with temperature and pressure (hence why I said @ STP), but this gives you an idea. If you have a lead foot or you hypermile, using this method you will get much more tailored results to your particular driving vs. asking others what kind of mileage they get.

One thing to note a lot of E85 isn't really E85 either, it could be a LOT less ethanol sometimes and yield better mileage (lower octane/performance). It's a very inconsistent fuel at least around here. So just how we mentioned gasoline is some variance between E0 and E10 there is a wide swing for E85 too. Get a tester kit to see what's coming out of your pumps, they're like $6 for one of the E85 kits. Furthermore your car will not always run at lambda 1.0.

EDIT: Had to fix math, it's still early lol.
Why's nobody giving this guy a standing O for being bang on ? His math is solid, it's based on FACTS. And those of yous who say your getting 13-16 mpg on E85 in normal driving are full of shit.
 

Zelek

Well-Known Member
Joined
Feb 11, 2016
Threads
101
Messages
4,763
Reaction score
4,621
Location
Round Rock / Hutto, TX
First Name
Matt
Vehicle(s)
2021 Mustang Mach 1
Averaging 12 or so with city driving mostly.
Sponsored

 
 




Top