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Old 12-02-2022, 05:52 PM   #1
Scooby Specialist
Member#: 134764
Join Date: Dec 2006
Chapter/Region: RMIC
Location: Lindon, Utah
04 sti
java black pearl

Default 5 year old e85 in gas tank

I blew up my motor 5 years ago and parked the car. I'm going to start rebuilding it but it has e85 in it from 5 years ago.

What steps would you take to clean everything out?
Do you think it has cause damage to the tank, fuel pump (dw301) and fuel lines?

I wanna somehow flush everything before pull the motor so its flushed before the new components go in.

My plan is to drain tank and flush lines.
Send fuel injectors in to get cleaned.
New fuel filter.
Inspect the inside of the tank when I install a new fuel filter.
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Old 12-02-2022, 07:24 PM   #2
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Member#: 458809
Join Date: Nov 2016
Chapter/Region: NESIC
Location: Boston
05 blob, 02 bug


What kind of fuel lines do you have? I'd personally replace those lines and probably the pump for peace of mind after flushing everything.
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Old 12-02-2022, 07:33 PM   #3
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Join Date: Oct 2022

ethanol converts to acetic acid and water (vinegar) if it sits in the presence of oxygen.
it takes a long time but eventually it converts

C2H5OH + O2 >>> CH3COOH + H2O
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Old 12-02-2022, 07:33 PM   #4
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double post bug
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Old 12-02-2022, 07:37 PM   #5
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Member#: 515308
Join Date: Jun 2020

I bet there is a disaster in there. When we went to e15% our tanks turned into a pile of rusty crap. It didnít take 5 years either, I imagine E85 would be infinitely worse

Going ultra low sulfur diesel turned those tanks into algae ponds
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Old 12-02-2022, 11:58 PM   #6
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Member#: 193940
Join Date: Nov 2008
Location: Philly
2004 WRX STI Black
RalliSpec Shortblock


Not 100% sure about gas tank, but the E85 corroded those injectors for sure. Well depending which ones you have. For example, ID2000 injectors are E85 compatible, but they should not be exposed to stagnate E85 for a period greater than one week. The reason being water absorbed by the ethanol can corrode the internals of the injector and possibly cause them to stick or reduce flow capacity.

The fact is, if neglected for a long enough period of time, the E85 in your car's fuel system will absorb enough water to corrode steel and aluminum. To prevent this, never allowing E85 to sit in the fuel system longer than a week. If you anticipate there being a longer sitting period, flush the system with real gas. I will be using E85 on my track build and have been doing lots of reading. I'm planning to use E85 on the track, but will have to fill it up with gasoline before I store it for the season.

I would drain the e85 from your car as much as you can from the drain plug on the gas tank, fill it up with regular gasoline and pushing it through the injectors before you ship them out for cleaning. It's messy but can be done without engine running.

I'm in the same boat but with 5 year old gasoline.
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Old 12-11-2022, 05:17 PM   #7
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Member#: 121212
Join Date: Jul 2006
Chapter/Region: SWIC
2007 Sti Limited
Urban Gray Metallic


If you use fuel stabilizer it will extend the life of the fuel and block the corrosion. They make a marine fuel stabilizer for ethanol fuels as well. The ethanol does not go bad. The 15% gas does. The ethanol will absorb moisture, ie water, depending on your humidity. The best way is to keep the tank fuel. That reduces the air to fuel ratio in the tank. Meaning the fuel will absorb as much as it can and then reach an equilibrium and absorb no more. Until you open the tank again. My Sti sat for nearly 9 years with no issues. I replaced the pump "just in case" but the injectors are fine.

I would drain the fuel and replace it if you did not use stabilizer. Also once you get it running run a couple of bottles of Redline or Royal Purple fuel cleaner just in case. (Both have the max.amount of PEA of all the fuel cleaners.) That's what I did and have no problems with the fuel system.
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