E85 Question

I had a question regarding E85 on a 2013 Mustang GT (although I imagine it could be applied to any other vehicle as well).

I’ve been considering switching over to E85, it’s pretty decent in the spring/summertime in terms of ethanol content where I live in Maryland. However, my tuner told me I could safely run as low as E70 if I were to have them tune my car for E so it should be fine even in the winter when ethanol content in E85 is lower than usual.

In order to run E85 on my car all I need is bigger injectors (47 LU) and a tune.

My question is:

Since E85 draws in water faster than regular gas especially when sitting for long periods of time, I’ve heard you should run a tank of 93 through the tank (After switching tunes of course) once every couple months to keep water out of the system and everything clean.

Is this only necessary if the car is rarely being driven? Or should regular pump gas be run through the car on a periodic basis (after switching back to a pump gas tune of course) regardless of how often it’s being driven? Is it safe to run E85 year round without ever cycling with a tank of pump gas every so often as long as the car is driven at least once a week or so?

Here’s a question: what’s your plan or purpose in wanting to run E85 gasoline?

E85 has less chemical “energy” than straight gasoline, or even E10 gas. Meaning… on a miles per gallon basis, you’re going to use more E85 to go the same distance as E10. It may be cheaper per gallon, but you’re going to need more gallons of it.

So… it’s going to be more expensive, or at least not cheaper, to run E85 vs E10. Plus, it sounds like you have some experience with a “tuner”, which makes me think you’re trying to squeeze some more “performance” out of your car.

Don’t do this to impress your buddies. It’s only going to cost you.

1 Like

You can run E85 without running a tank of 93. The E85 will carry the water out when used. The normal 93 octane E10 brings nothing to your car so why switch back? Neither fuel “ages” as well as ethanol free fuel. Even with weekend only use, you’ll go through E85 fast enough to keep it fresh.

Carry your tuner tool with you all the time. E85 is not available everywhere ( at least where I live) so you might need to switch it back to 93 to get home. Be sure you have a 93 octane tune for those 47 lb injectors.

Because E85 is not as strong of a solvent as regular gas therefore wouldn’t it cause more deposit buildup in the fuel system? I’ve also heard that E85 “supposedly” corrodes plastics and seals and doesn’t lubricate the fuel pump like regular pump gas, which is why people say to run a tank of regular gas once in a while. I’m not sure if this is true, there is so much conflicting information on the internet.

The end goal would be to make more power, as long as the only cost would be having to fill up more often that’s a price I’m willing to pay

How much more power? Without increasing the compression ratio or adding a turbo I don’t see how E85 can lead to much of a HP increase.

E85 does corrode non-compliant rubber and plastic parts. If your car did not come from the factory as a flex fuel car then you may need to change any parts wetted with gasoline that aren’t ethanol safe. Assume that anything nonmetallic needs to be replaced unless you can find specific information from a reputable source, like Ford. Using E85 without acceptable fuel system parts will eventually be a disaster for your injectors.

I’ve done a lot of research and 11-14 5.0 coyote only needs upgraded 47 LU injectors and a E85 tune to safely run e85. The rest of the stock fuel system “can” handle e85 as it is but as far as longevity is concerned it was still unclear as to whether or not I should cycle 93 through the tank every so often for reasons mentioned earlier or if it’s unnecessary.

I already have cold air intake and long tubes/high flow cats so e85 should add around 15 rwhp or so from what I understand. Not too bad for just upgrading injectors and re tuning

Engine Masters only gained about 12 HP at the flywheel with E85 vs 91 octane on a 530 HP 6.2L LS crate engine, so good luck…

Because E85 is a STRONGER solvent than gasoline… Internet nonsense

Yes, true because is is stronger solvent…

Yes, it does lubricate and cool the pump… and running a tank of E10 every few fillups isn’t going to do squat for that.

Because it IS the internet…

You will gain power on E85… It allows more spark advance because of the higher octane. It also cools the intake flow which allows even more spark advance and makes more power. All at the expense of 20 to 30% less mpgs.

I’ve tested up to 30% ethanol mix in my tank. It pushes the stock 34 lb injectors up to about 85% capacity at full throttle. Long Term Fuel Trims also go rather positive adding more fuel, too. Seat of the pants feel and measurements show an increase in horsepower of roughly 10% at the wheels.

It is impractical to run E85 where I live because there are so few stations that sell it. I’d run a mix and consider an E85 tune if the race track I do trackdays at had any stations nearby that sold E85.

Any way you can get a baseline performance number and then see what the E85 does? 1/4 mile time, etc?

Just get a flex tune, no need to overcomplicate things.

I wanted a flex tune but all the major mustang tuners stopped doing them for some reason

I suspect that is the need to widen the fuel trims beyond the error boundaries built into the engine parameters which may then violate the EPA certifications.

Here’s where I think the problem is… Fuel trims are only allowed to vary so much… +/- 25% (some less). Any more and it sets an error code and a check engine light. This is to let you know the car is out of compliance and needs repair.

If the car is tuned for E10 gasoline, the O2 sensor is going to force a Lambda of 1.0 (air/fuel ratio of 14.0) and theoretically should have a long term fuel trim of zero. Now throw in E85. To reach the proper air fuel ratio, the injectors need to send 30% more fuel to reach a Lambda of 1.0 (air/fuel ratio of 9.8) throwing the long term fuel trim to about +30.

In order for that to not set an error and check engine light, the flex tune would need to remove or widen those limits beyond factory limits. I think the EPA would have a problem with that. They already have a problem with ANY tunes… No one wants to poke that hornet’s nest any more than they already are.

1 Like

Here’s what they got on Engine Masters using a variety of fuels:

1 Like

Again… what is the point of doing this change to your car, which could potentially cost you more money in the long run?

Your “tuner” buddies that you’re going to brag to won’t help you pay for the potential damage.

Sorry, I don’t mean to sound harsh. But I was a young man once, and looking back, I threw away a lot of time and money with car stuff that I shouldn’t have. The best thing you can have is a paid for, reliable car. Anything else is just throwing money away. Just trying to share some wisdom.

OP, are you certain the materials used in your car’s construction are fully compatible w/E85?

And here is the episode…

I don’t recall them saying much about the tune that Westech used in the engines to achieve those results. Also, wasn’t that test with a carbureted engine?

1 Like

No, it was a LS fuel injected engine… Off camera the timing was always optimized for the most power, but if the engine runs best at X total timing, octane does not change that as long as it has enough octane to support the engine timing needs… As Brule likes to say, an engine wants what it wants…

Watch the video that Texases and I are talking about…

But yes the engine had to be tuned for E85…

@George_San_Jose1 Yes I am sure. I know a few people personally that ran e85 on 11-14 5.0 with nothing but 47 lu injectors with no issues. However everyone I know with this exact car running E85 has only been running it anywhere from a few weeks to a few months hence why I asked my original question about it being safe long term without cycling pump gas

@ledhed75 I understand where you are coming from. You could argue every mustang I owned before this one was a waste because I just ended up selling it for less than what I put into it. And from a purely monetary standpoint yes it was a waste. But I got enjoyment from owning, working on and driving them so not a waste in my book.

At the end of the day money is for 2 things: surviving and doing what makes you happy. Well modifying and working on my car and adding things to make it go faster and seeing tangible results makes me happy. I don’t modify my car to impress other people as the primary reason, although that comes as a bonus I suppose. I don’t believe adding E85 will compromise reliability SO LONG AS I got a clear answer on what I originally asked which was essentially “Is it ok to be running e85 all the time” and assuming the cars fuel system can handle it, which mine can with just a simple injector upgrade and tune, the general consensus seems to be yes, it is ok and there shouldn’t be any problems or reliability issues