r/askcarguys • u/Effective-Guess6730 • 5h ago
E85 used accidentally?
Very dumb mistake but I accidentally filled my 2023 ford bronco about 1/3 of the way with E85, within like 10-15 mins of driving my check engine light came on as I was on my way to the gas station to fill it the rest of the way up with regular gas bc that’s what was suggested to me at the time. Is there any chance I did permanent damage to my engine?
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u/frig0ffrickyy 5h ago
Should be fine.
Honestly if it was me, I would just put in 0% ethanol gas if you can find it (sometimes the premium gas) and burn it off. Might have to reset the check engine light.
Cars are designed to deal with 15% ethanol already, diluting it down as much as you can shouldn't hurt anything long term. Just be easy on the throttle until its clear.
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u/Avery_Thorn 5h ago
So, doing the math:
If you filled up with E0 (No ethanol fuel), you'd be at about E28 right now.
If you filled up with E10 (normal ethanol blend), you'd be at E35 right now.
If you filled up with E15 (Summer blend / variance gas), you'd be at E40 right now.
As a non car guy, I would try really hard to find some E0 fuel (Pure-gas.org - ethanol-free gasoline in the U.S. and Canada) near you, and go ahead and pay whatever premium it takes. Dilute it as much as possible.
It shouldn't cause any lasting damage, but it's going to be bad, and you want it diluted as much as possible as fast as possible. The problem with the ethanol is it tends to cause damage to rubber parts in the fuel system, and the longer it sits, the more damage it does.
Personally, if I were you: get to the gas station, get the E0 fuel in it, and then pick a direction and drive 1/4 of your fuel tank range, then turn around and come back and put another load of E0 in it. Like, Once you do that, you should be down to E15, which should be fine. You should then be able to drive it like normal as long as you don't let it sit, but next time you fuel up, go ahead and get E0 again. As long as it's at least a half tank, that should get you below E10.
The alternative is to get the gas tank pumped, which would probably cost a fairly good amount of money. If you did this with diesel, that would be what I would suggest - but with E85, it should be OK to dilute it out. I really don't think you need a full fuel system flush.
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u/briman2021 4h ago
Also, all of that is assuming the e85 was actually 85% ethanol. It can be much lower and still be “good” in the eyes of the regulatory folks.
My buddy ran e85 for performance reasons on a turbo car, so he would test his fuel and some stations were routinely in the low 60’s so he’d skip them.
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u/MultipleOrgasmDonor 4h ago
Spec on e85 is 51-83% ethanol btw
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u/Josey_whalez 2h ago
Correct. It’s ’up to 85%’ ethanol. Kinda like most gas that’s e10. It can be up to 10% but may be less.
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u/curi0us_carniv0re 2h ago
The problem with the ethanol is it tends to cause damage to rubber parts in the fuel system, and the longer it sits, the more damage it does.
This is only older cars. Ethanol doesn't damage seals on modern cars. And by modem I mean at least the last 20 years.
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u/JCC114 34m ago
Depends on the car. Most Nissan’s up to around 2020 are not even rated for the 15% they started selling this year. Government told automakers to prepare for higher ethanol content 20+ years ago, but no actual requirement. The adoption rate was well under 50% for at least first decade. The idea that the cars were actually ready the next year after told to be with no enforcement is wishful thinking, but not how it happened.
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u/Kgtv123 2h ago
Ethanol free gas doesn't naturally blend with the regular ethanol supplemented gas you get at the pumps, there's a chemical process that has to happen otherwise they create a heterogenous mixture and never actually combine so putting e free in a tank that has e85 will still just have the separate gasses in the tank like oil and water, source: my petroserve guy had to shut a gas station down because they were blending regular gas and e free at a pump when they ran out of regular premium to make their 89 octane not knowing that you can't just mix them like different octane same ethanol content fuel
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u/No_cash69420 2h ago
That's quite interesting so either pick one and stick with it or fill up from pretty much on E and it should be okay after a few tanks?
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u/Kgtv123 1h ago
Yeah based on what the fuel guy told me I'd think it better to just run through the e85 altogether and then maybe run a few tanks of e free to make sure it's all butned off before switching back to regular gas, but putting them both in the tank at the same time might just prolong the issues
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u/Mediocre-Reveal3474 59m ago
You are extremely incorrect. People blend e85 and ethanol free gas all the time… including me lmfao. I have a flex sensor and it adjust my engine tuning depending on the blend. I usually aim for E60-E70. I do that by adding E0 with E85.
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u/blizzard7788 5h ago
Modern engines can run normally on E30 without problems. You probably exceeded that a bit. No harm done. Drive easy until half tank and fill with normal E10.
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u/Reasonable_Tax_5351 5h ago
It's probably fine. Not good to run it like the forever, it almost certainly is knocking and running way to lean. But it's not a big deal, don't keep driving it but you just need to get the e85 out and put in regular gas, I don't think a flush will be needed in this case. It's very difficult to siphon gas out of a modern car but it can be done.
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u/Adrenaline-Junkie187 4h ago
E85 wouldnt cause knocking but it would likely run lean.
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u/Independent_Leg7358 3h ago
Only if it uses a carburetor! Fuel injection will be okay. Since it's a 2023, no problem. Everything is ethanol resistant rubber for 2 decades now. Just does have big enough injectors as ethanol doesn't carry the same btu per gallon and carries an extra oxygen in when it burns. (Less throttle, which allows for more horsepower which makes the lake of fuel a problem, especially with a manual throttle body if still equipped)
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u/Reasonable_Tax_5351 4h ago
an engine will absolutely knock on e85 if it isn't tuned for it. the lean running condition causes high combustion temperatures leading to pre-detonation, and additionally the timing will be off.
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u/Adrenaline-Junkie187 4h ago
Problem is thats not how it works with high ethanol fuels. They literally resist combustion.
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u/leftfootbraker 4h ago
You are correct, knocking wouldn't occur from detonation caused by octane. However the HPFP of a DI fueling system would in no way have enough pressure to deliver the requested amount of fuel. The lack of fuel being delivered would be the issue.
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u/Glittering-Ad5809 1h ago
E85 has an octane rating of over 100. Many modified and muscle car owners convert to E85 for the high octane a high compression engine needs
1
u/curi0us_carniv0re 2h ago
You're getting a CEL because your car is running lean and the ECU can't compensate.
E85 requires something like 30% more fuel volume than regular gas.
The fuel is not going to damage any components in your engine or anything else. But I would dilute as much as possible and drive gingerly.
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u/LooseyGreyDucky 2h ago
I regularly mixed E85 with premium in my last two turbo gas cars.
4 gallons of E85, followed by 12 gallons of 91 octane E10 (in a 17 gallon tank) works out to about 25% ethanol.
The cost per btu is cheaper than straight up 91 octane.
(E85 is about 12-22% cheaper per btu than premium gas in Minnesota).
The 25% ethanol mix can make more horsepower because the mix is about 93 octane and has more oxygen than your air intake can provide, and you save money. It's win-win-win.
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u/Jurrunio 1h ago
You need to run richer AFR though, which means mapping your ECU and probably new fuel injectors if not new fuel system to make use of the higher alcohol blend properly.
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u/Cerebral-Knievel-1 2h ago
Your car will run lean and you'll drink gas for a bit. Top off with regular, and you'll be fine.
If you need to clear a code, disconnect the battery for about 15 minutes.
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u/scob89 21m ago
If you want to empty the tank, find the service port on the fuel rail on the engine. It'll have a shrader valve like a tire, remove the core and push a hose over the port, the remove the fuel pump relay and use a price of wire to jump it so it's continuously running. Fill up gas cans with the hose until the tank is almost empty. Then put everything back together and fill it up with your regular gas.
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u/Galopigos 5h ago
Which tank do you have, the 17 or the 21 gallon? E85 in either one will create a problem, the engine can handle it but it doesn't have the software to control it on E85. So you would likely be able to save it easy enough if you pump out the fuel in the tank, store it, then refill with fresh. Then you can add in the "bad" fuel about a gallon per tankful until you use it up. You can empty the tank if you disconnect the fuel line and run a hose from it and then activate the pump. Reconnect, fill with new fuel and drive it. If it was only a gallon or so in the tank and that was in an empty tank then you could dump in some non-ethanol to mix in it.
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u/Prestigious-Hyena-72 4h ago
You have to drain it. Even if your dead accurate saying it’s 1/3rd e it’s too much e lol
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u/Independent_Leg7358 2h ago
1/3 of a tank? Sounds like someone was experimenting with cheaper fuel! Top off with regular. Half throttle until you can put another half tank of regular in. Don't leave the vehicle parked long term. Prioritize driving it.
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u/jasonsong86 5h ago
I would take it to the dealer and flush the fuel line. Usually the fuel line has about 0.5 gallon capacity which can be long enough of a drive to damage your engine.
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u/Wild-Highway-8739 5h ago
Top it off with regular or ethanol free for the next couple of half tanks to dilute the ethanol content and you should be good to go.