When to use Flex fuel/E85?

Nick The Great · August 15, 2017

My 2007 was flex fuel and with my numbers/driving habits I needed 40 cents to break even. Which wasn't hard to do in the late 00's, but the price difference dropped with the price of crude.

I don't understand people bitching about E85 getting worse economy. Gasoline gets worse fuel economy than diesel and people are okay with that? Propane gets awful fuel economy,and they made vehicles for a while that ran on that.

I get that it's a cost/mile thing and that's fair. In fact, that's the only fair way to judge things.

I'm sad that I couldn't find any Flex Fuel trucks when I got this one, even though I hadn't run E85 in a while.

willyr1er · August 15, 2017

I used E85 for the first time a few weeks ago. Little worried when I was filling up since I have only used 87 Oct in the truck. E85 was about 30 cent cheaper. I did notice a big change in the truck, it felt much stronger. More Fun!

If I had e85 easy to get to for fill ups I would only use it. Loved using it and looking forward to finding it again!

Jsmith86 · August 15, 2017

I couldn't tell a difference in my wifes minivan but now I need to try it in my Silverado so I can see this difference I keep hearing about.

jhbrennan · August 15, 2017

Depending where you get information, it seems that running E85 gives you 20-30% worse fuel economy per gallon.

So to justify that you would have to buy it for the same discount. At today's price in my town that would be .45 - .67 cents per gallon.

So I would tend to agree with your friend that says you need to get it for at least 50 cents/ gallon less, otherwise you're just burning money.

I don't even know if my truck can burn E85. I know there's no "Flex Fuel" decal on the tailgate. I'm going to continue buying the regular gasoline with 10% ethanol blend they give me at every gas station.

Should have a yellow gas cap if flex fuel or some other designation near the gas cap.

Jsmith86 · August 15, 2017

Should have a yellow gas cap if flex fuel or some other designation near the gas cap.

Yea mine has a yellow gas cap

DougIrby · August 15, 2017

E85 makes a very noticeable difference when towing a travel trailer. When towing, I would be willing to pay more for E85 than I would when not towing.

newdude · August 15, 2017

Great info guys! I didn't think about using E85 when towing. I'll start experimenting with it. I have a few gas stations near my house that sell it. Would anyone buy E85 if it was the same price at 87 octane if you're about to tow a camper a long distance?

One thing to keep in mind if you are going to run it here and there, is to make sure you run the tank down to just about empty when switching back and forth. You won't notice any changes if you fill say at 1/2 tank as the E85 would be cut from the 87 and may skew the flex fuel sensor readings.

Jsmith86 · August 15, 2017

Yea I wondered about that.

RhinoGuy · August 16, 2017

My 15 runs noticeably better on e85. Shifts better too.

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x219c · August 16, 2017

Another thing to keep in mind when towing is this truck only has a 26 gallon tank. I've heard some say this leaves a less than desirable range on regular gas. It's going to be worse on e85.

I haven't had to tow any amount of distance for this to matter, but I had thought I saw people getting around 10 or thereabouts on e10. That's only a 250 mile range. I don't know what the mpg would be towing with e85. But let's say 7, just for arguments sake. That's only around 175 miles. Of course, these numbers change depending on what you're towing, and how fast.

If you like stopping often, may not be a big deal.

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Brian S. · August 16, 2017

In short, there's never a good reason to run it. It's normally used for big fleets. Companies that have a bunch of vehicles that don't drive long distances that don't want to buy higher priced fuel. Most of them actually have their own filling stations.

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The reasons to run it are:

1. It can be less expensive, depending on price vs E10. A person needs to check their mileage with a few tanks of E10 vs a few tanks of E85 to know what the ratio is for them. If you establish that you get 20% less mpg, E85 priced at 25% less per gallon saves 5% on fuel.

2. On GenV engines, the sensors adjust compression and timing for an approximate 10% increase in horsepower and torque. That is a pretty cheap way to get 10% hp/tq even if E85 was priced the same, and it's something you can do to increase power that is fully warranted by GM.

3. E85 uses corn produced by American farmers for 85% of each gallon, which not only supports American labor, but reduces the trade deficit. Over half of the E10 gas is produced in foreign countries:

https://www.eia.gov/tools/faqs/faq.php?id=727&t=6

There is a legitimate argument that production of E85 can't happen in a cost effective manner without governrnent subsidy, but as it is, the government is subsidizing. (probably to reduce dependence on foreign oil.

These are all good reasons to burn E85 in my opinion.

I could really notice the difference in the 2014 Silverado 4.3l I had, made it almost identical in power to the 2010 5.3l I replaced. I don't have the option in my current 2017 5.3l.

jhbrennan · August 16, 2017

Anyone know definitively if my 2017 Yukon Denali 6.2l is flex fuel. No indications near the fuel filler or in the owner's manual to let me know. Thanks.

Jsmith86 · August 16, 2017

Anyone know definitively if my 2017 Yukon Denali 6.2l is flex fuel. No indications near the fuel filler or in the owner's manual to let me know. Thanks.

Man I have no clue.

cmysstailights · August 16, 2017

Anyone know definitively if my 2017 Yukon Denali 6.2l is flex fuel. No indications near the fuel filler or in the owner's manual to let me know. Thanks.

No the 6.2 is not compatible. Requires the sensor and a tune. Fathoms me as to why it's not available on that motor

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dorkweed · August 16, 2017

I've been experimenting with E15 the past 4 tanks. I've been getting the same mpgs as 87 octane which is E10; however E15 is 10-15 cents cheaper per galon and comes in at 89 octane which isna steal because 89 octane here runs 30 cents more than 87.

As for E85, i ran that 3 years ago and the calculus i came to was that at a minimum E85 needed to be at least 25% cheaper in price than 87 to be comparable to 87.

I just filled up with E15 about 15 minutes ago. It said 88 octane on the pump; not 89 like mid grade E10. The E15 was .10cents/gallon less than 87 octane E10. Just saying.