E-85 Fuel

goat226 · July 18, 2008

hey all,

i just got a 2006 gmc sierra 1500 crew cab z-71, with a 5.3 v-8. it can run on e-85 fuel. around here (if you can find it) its about 50 cents cheeper. i herd you use it up faster than regular gas. is this true? and do you have to be on empty to fill up with e-85, or can you mix it? thanks.......ed

theno1prince · July 18, 2008

I've seen people experience anywhere between a 12% - 20% drop in mileage. It depends on driving condition, driving habits, etc. You can mix it with gas as much as you want as it already has a 15% gas content (e85 means 85% ethanol, 15% gasoline). All it will do is become a lower concetration of ethanol.

If you want it for cost savings, you're probably not going to notice any. Around here it is about 15% cheaper than gas but I've noticed about a 15% drop in gas mileage which eliminates anything that I saved over gas.

The thing I do like about ethanol is that it does a really good job of cleaning out your engine (it breaks up carbon deposits quite nicely) and it burns about 300% cleaner than gas. It is also about 105 octane. Now I just want enough e85 stations available that I can build a car with a 13:1 motor to run soley on e85. Now that would make it worth any drop in gas mileage!

MI 99XPL · July 18, 2008

hey all,
i just got a 2006 gmc sierra 1500 crew cab z-71, with a 5.3 v-8. it can run on e-85 fuel. around here (if you can find it) its about 50 cents cheeper. i herd you use it up faster than regular gas. is this true? and do you have to be on empty to fill up with e-85, or can you mix it? thanks.......ed

Congratulations on your purchase Ed!

Yes, you'll use more gallons of E85 than you will gas. But since it's less money, the best way to compare the 2 is cost per mile. Here's the math.....

cost of fuel / MPG = cost per mile.

figure out both gas and E85, then compare the cost per mile.

I recommend running a few tanks of E85 and a few tanks of gas through to get you MPG for each type. This takes into account your driving habits and gives you real numbers to work with. The "general" information you hear and read about for "everybody" in the US, is just that, general information. It's your money, be specific!

You don't have to be empty to fill up with either E85 or gas. The PCM will adjust accordingly. But I have read that some people don't see a difference in the MGP read out until they burn a few tanks of mix (that's switching in either direction). So if and when you can, and if you care, waiting until the tank is low might be better. And I stress might. It's not going to damage anything with your truck.

Nick The Great · July 18, 2008

If you check out the E85 section on this board, you'll find some good info.

A fellow by the name of sparkstech posted this thread, which is now a sticky.

http://www.gm-trucks.com/forums/index.php?showtopic=78169

He provided way more detail and technical info than you'd care to know, but it is very informative. But basically he says, and even posts it at the bottom,

TURN THE KEY OFF
USE MORE THAN 3 GALLONS
DRIVE 7 MILES OR MORE

I've been running E85 constantly since April. I got the truck in March, and did some experimenting. I lose 2-3 mpg both on the interstate and in the city. So you're talking going from 14 to 11 in the city. (A lot of stop and go ) But in the Des Moines metro, if you're careful, you can get E85 for 80 cents to almost a dollar cheaper sometimes.

goat226 · July 18, 2008

thank you all so much for the info on e-85. it will be a great help....ed

huero626 · July 19, 2008

My 2007 Suburban can run E-85 but one of the main reasons I don't run E85 is because I have never seen an E85 gas station and another reason is because I heard that your fuel economy goes down, so I would rather run 87 octane gas and get better mileage even if it is more expensive.

Sepiroth · July 19, 2008

My 02 Suburban is a Flex Fuel. I have used E85 as it is over 1.00 cheaper than regular Petro. I average between 12.88 and 13.91 miles per gallon using mixed highway and city driving. I typically get about 220 and the highest was above 280 miles before I choose to fill up using about 16-high 19 gallons. I could use the whole tank full and see how many miles I could get out of a 30 gallon tank but I dont fell like filling up 30 plus gallons with E85 that cost $3.159.

fbachman · July 19, 2008

I have crunched the numbers many times.

Run your numbers.

Assume a 20% decrement in fuel economy with E85 over gas. (If you have the actual numbers for your vehicle, it will turn out a little different, of course)

Determine your miles driven per year/month, whatever interval makes sense for you.

If your truck gets 15mpg on gas, assume it will get 12mpg on E85 (this is due to the substancially lower heating value of E85).

Now you can caluclate your cost per mile, assuming you know the cost of both a gallon of gas and a gallon of E85.

If I recall, the E85 cost has to be SUBSTANCIALLY lower than that of gasoline to, even, come out on par.

Example:

15mpg gas, 12 mpg E85

If gasoline costs $4 per gallon, E85 must cost $3.20 per gallon to break even, less to actually incur any savings at all.

If gasoline costs $4 per gallon, and E85 costs $3 per gallon, you save $166.67 per 10,000 miles driven.

If gasoline costs $4 per gallon, and E85 costs $3.50 per gallon, E85 costs you $250 MORE per 10,000 miles driven.

Throw it in excel and crunch it. Depends on what you can get gas and E85 for in your neighborhood/city.

Tried to upload an excel file... didn't work.

Send me a PM and I'll e-mail it to you, if you wish.

EDIT: Added the following chart to determine the break even price of E85 vs. Gas Cost

fbachman · July 19, 2008

Added a chart for reference...(see above)