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Lots of people have run E85 using the stock tank, I have never heard of it being an issue.
 

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Looking for an answer so I know if I need to go to a fuel cell
I’d suggest caution here. E85 is corrosive. You might not notice a problem right away, but that’s how corrosion works. As a point of background, I worked at GM for over 30 years. Among my many jobs, I headed a Powertrain Product Planning organization that among other things was responsible for the rollout of E85 applications. That included working with the various vehicle subsystems (tanks, pumps, filters, fuel lines) and engine components (valves, valve seats) to make certain they were sufficiently protected against ethanol corrosion. E85 wasn’t even in play during the lifecycle of SW20. Combine that with the fact that during the implementation of E85, Toyota was NOT in favor of E85 as a fuel. So the likelihood that AW11 or SW20 tanks are robust enough to protect against ethanol corrosion is slim to none. You’re rolling the dice.
 

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E85 by itself isn’t corrosive, but moisture in the tank combined with it to form acids which greatly accelerate corrosion.

I think it’s fine to run on zinc plated steel tanks of this vintage, but I’d advise against long term storage with high ethanol content. I try to “pickle” my tank with a few tanks of E10 before storing the car for winter. Gets it down below 20% ethanol quickly (pump gas is consistently 11-12% ethanol here too, which is the same as what I saw in TX).
 

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E85 by itself isn’t corrosive, but moisture in the tank combined with it to form acids which greatly accelerate corrosion.

I think it’s fine to run on zinc plated steel tanks of this vintage, but I’d advise against long term storage with high ethanol content. I try to “pickle” my tank with a few tanks of E10 before storing the car for winter. Gets it down below 20% ethanol quickly (pump gas is consistently 11-12% ethanol here too, which is the same as what I saw in TX).
This is to some degree consistent with the point I was trying to make. Automakers had to adjust to make systems compliant with E10, which is used in many more states than those where it isn’t. But a few years ago when EPA was looking into bumping up to E15, automakers had a screaming fit. Products were engineered and validated for E10. Unless they were already validated for E85, they wanted no parts of anything at E15. So for products that were engineered in the late 80s, early 90s, they were engineered to an E10 expectation, not E15 and certainly not E85.
 

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OE validation is very different than “it won’t work at all.”

Generally these plated steel gas tanks are fine for E85 usage in a well cared for enthusiast car. I’ve never seen them have more tank corrosion over time than E10 usage as an anecdote.
 

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OE validation is very different than “it won’t work at all.”

Generally these plated steel gas tanks are fine for E85 usage in a well cared for enthusiast car. I’ve never seen them have more tank corrosion over time than E10 usage as an anecdote.
All I can say is that there is a long list of vehicles where we could not implement E85 because some part or another of the fuel system was never E85 corrosion proofed and the business case for doing so didn’t merit the cost. This was in a company that needed E85 credits to meet CAFE targets. Toyota did not need E85 credits so none of their vehicles were engineered to be E85 compatible. If you want to gamble with your car so be it. I can’t say that E85 will damage the tank or the fuel pump or the fuel filter or the injectors, or the valves or the valve seats. But I sure as heck can’t say that it won’t. I can only say that for GM and other brands that produced FlexFuel capable vehicles, those are the parts that received special processing to ensure long term durability and corrosion resistance.

FWIW, I run E85 in my Camaro SS, so I am not anti-E85. I just know that the important components are already E85 capable and that it came from the factory a fuel sensor and a tune away from being E85 capable.
 

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From eFlexFuel.com…

Vehicles produced before 1994 didn't have to be compatible with ethanol-based fuel. That means the stock parts in these cars weren't always "immune" to ethanol. Ethanol can corrode some materials, including some types of:
  • Plastic
  • Rubber
  • Some metals
When a vulnerable material is exposed to ethanol, it deteriorates over time. That can lead to some pretty serious engine damage. Back in the old days (pre-1994), E85 could eat away at some engine components. Most vehicles produced in and after 1994 are immune to ethanol. Since 1994, it has been US federal law that vehicles must be compatible with ethanol. So engine damage caused by E85 hasn't really been an issue since then. Yet, this myth still stuck around. Here are some of the other reasons for the persistent myths about ethanol damaging the vehicle:
  • It’s often confused with methanol that is highly corrosive and will eat the plastic parts within weeks.
  • It’s often confused with ethanol racing fuels that can have corrosive components.
  • It’s often used in vehicles that are not made for it, like normal gas-powered vehicles without a kit.

To be totally clear, even though I personally wouldn’t trust pre-1994 Toyota fuel tanks to be E85 friendly, (because they didn’t engineer for ethanol content until required to for 1994) the tank would be the least of my concerns. I’d worry more about the in tank fuel pump, the valve stems and valve seats and the rubber parts of the fuel line.
 

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Most people going E85 are only going to have stock fuel tank and valve seats at that point. IMO, the valve seats are likely a long term issue if at all. Most E85 MR2s are not going to see 100k mi.

I’ve run E85 for years on a ‘92 Nissan and my ‘93 MR2. Seen no issues. Just don’t run 30 year rubber fuel lines filled with E85. That sounds like a bad idea even if they were “compatible” when new.
 

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Most people going E85 are only going to have stock fuel tank and valve seats at that point. IMO, the valve seats are likely a long term issue if at all. Most E85 MR2s are not going to see 100k mi.

I’ve run E85 for years on a ‘92 Nissan and my ‘93 MR2. Seen no issues. Just don’t run 30 year rubber fuel lines filled with E85. That sounds like a bad idea even if they were “compatible” when new.
I look at it like this. We all know that smoking causes lung cancer. Some people smoke their entire lives and never get lung cancer. Some people smoke and early on get cancer. Some even suffer horrific, yet avoidable deaths. All know the risks going in. We all know that our cars were produced before E85 was introduced, so they are not engineered to endure E85. Some people will run it and they’ll be fine, like people who smoke and don’t get cancer. @DefSport is likely one of those. How many are out there that have suffered catastrophic failures and haven’t traced the cause back to E85? And how many who have traced it back would openly admit it? All I’m saying is know the risks, then do what you want with that knowledge in hand. Even the lobbying group that is pushing the cause for E85 acknowledges that it is dangerous for vehicles produced before 1994 (I quoted them in post #8 in this thread). We can accept what they say is knowledge, we can reject it out of hand, or we can proceed forward knowing that there are risks.

I run E85 all day and all night in my Camaro. But it came from the factory with hardened valves and seats, a capable fuel tank, fuel pump and corrosion resistant fuel lines. All I had to do was add a FlexFuel sensor and get it tuned for E85. I will not be running E85 in my MR2, at least not until I need to do a build on the engine and can replace the valves and seats with something sufficiently hardened.
 

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Pretty sure the overall risk to the car is less than the 350+ rwhp most people would be pushing through their 200 bhp car when running E85.
As with modding a car from stock, it’s probably not going to do it as long or as trouble free as if it was 100% stock.
 

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Discussion Starter · #12 ·
This is really
Most people going E85 are only going to have stock fuel tank and valve seats at that point. IMO, the valve seats are likely a long term issue if at all. Most E85 MR2s are not going to see 100k mi.

I’ve run E85 for years on a ‘92 Nissan and my ‘93 MR2. Seen no issues. Just don’t run 30 year rubber fuel lines filled with E85. That sounds like a bad idea even if they were “compatible” when new.
This is a late response but this is a k24 car. All new everything going in
 

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This is really

This is a late response but this is a k24 car. All new everything going in
You may want to consider popping into a Honda forum and asking their experiences with E85 on stock engines.
 
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