Q&A / Tech

Ask Away! with Jeff Smith: The Pros and Cons of E85 in Performance Applications

Old guy up in Canada scratching his head and wondering:

A: Is the oxygen in ethanol as hard on aluminum parts as the information available on the web says it is?

B: Can the corrosive effects be managed by adding materials to the aluminum or the fuel to offset the damage?

C: Or am I as the wife says just spinning my wheels … she also thinks that at 68 I am too damn old to go racing – chuckle.

Thank you for your time


Jeff Smith: We’ll assume that you are asking about the corrosive effects of ethanol as it relates to E85, which is 85-percent ethanol and 15-percent gasoline. This really comes down to advantages versus the disadvantages of E85. Because your questions deal with the disadvantages, let’s start with those.

Much of the talk about ethanol relates it to the damage done by alcohol to aluminum parts. Sometimes people say that ethanol is just as nasty as methanol. This is not true for several reasons but there is some validity to the point. As anyone who has ever sampled a mixed drink, alcohol mixes very easily with water. In fact, ethanol has a very high attraction for water and will pull this water directly out of the atmosphere. In E10, phase separation can occur when more than 0.5-percent (roughly 4 teaspoons of water per gallon) is absorbed into the gasoline/ethanol mixture. With higher mixtures of E85, it will take over 4 percent of water for phase separation to occur, and this is quite a bit of water. That’s 5 ounces of water per gallon, which is a lot.

Once enough water is mixed with ethanol and gasoline, the water separates the alcohol from the gasoline and this separation begins to contribute to corrosion in the system. This issue seems to be directly related to how long the fuel is allowed to remain in the tank, lines, and–if used–carburetor. I spent a whole day reading several white papers and corrosion reports about the effects of pump fuel (10 percent ethanol), which is a commonly-used octane booster. From these papers, it appears that when used on a semi-regular basis, the corrosive effect of water from phase separation appears to be very minor. It is when higher levels of ethanol and water are allowed to sit in a vented tank for periods extending beyond 60 days that bad things begin to happen. (see our story on Ethanol and fuel additives you can use during extended storage.)

Continuous use of E85 fuel will minimize the amount of water in the fuel. I read a report where the author purchased a Harley motorcycle “with only 9,000 miles” on the odometer and backed up his story with a photo of a badly corroded fuel pump assembly. What he didn’t mention was how long the Harley had been sitting, unattended and that a low fuel level also contributed to the issue. If the bike was also housed in a humid region, this would also contribute to corrosion. This was in reference to E10 pump fuel. The point is that the corrosive nature of water that has phase separated from the rest of the fuel in a tank barely one quarter full could cause these problems.

So the question becomes is E85 fuel so nasty that it will eat your fuel system in a matter of months as mentioned by all this negative press? I’ve been interested in this same question since my first stories on E85 fuel dating back to 2006. I’ve interviewed many racers and street enthusiasts who use the fuel in their street cars. Most of these E85 users live in the Midwest where E85 is easily found and is inexpensive. They’ve told me the only thing they do differently compared to straight gasoline is to pump the remaining E85 out of the fuel tank and replace it with regular pump gas and add some kind of aftermarket fuel stabilizer like Stab-il, Fuel Guard, or Driven Racing Oil’s Carb Defender additive. These enthusiasts report that they do this anytime the car will be stored for more than 30-45 days, especially if they live in a high humidity region like the south or Midwest.

Aluminum is susceptible to corrosion and we’ve probably all seen evidence of what methanol can do to aluminum fuel fittings if the fuel is stored for even a short period of time. However, anodized aluminum fittings tend to resist this corrosion. This appears to be related more to electrolysis than to water. Late model cars long ago converted to plastic fuel lines for all production vehicles and this was an indirect response to the increase in alcohol content of fuel–along with the fact that plastic also is far less susceptible to venting issues compared to rubber fuel lines. If you are planning on using E85 as a main fuel source, you might also consider converting the fuel lines over to what is called PTFE hose, which is a form of plastic that is impervious to all fuels. Several companies including TechAFX, Goodridge, Earl’s, and Brown & Miller make this hose. The hose is expensive and requires dedicated fittings, but short of physical damage, it will outlast your car.

So now let’s run through a short list of advantages to why you would want to put up with all the hassles of using a fuel like E85.

One outstanding area where E85 fuel works well is for a supercharged or turbocharged application. First of all, pump E85 has an octane rating of roughly 105. But even more important is that E85 has a very high latent heat of vaporization. This means that when it evaporates, it removes heat from the surrounding air. Let’s give you a real world example.

I did some testing on Ken Duttweiler’s dyno several years ago. The engine was a mild little 355-cubic-inch small block Chevy with a small Magnuson supercharger that was modified to locate a carburetor on the top (Magnuson doesn’t sell this but you can find an even better version from Edelbrock). Our small block used 10:1 static compression and the blower produced roughly 8 psi of boost. On gasoline, we would have had to use a very high octane fuel–probably around 115 octane. Instead, we ran the engine on E85. With an ambient air temperature of 70 degrees, the temperature just below the carburetor hovered below 40 degrees and at 8 psi, the discharge temperature below the blower was a mere 91 degrees F. On gasoline, that temperature would be closer to 150 degrees F. That low inlet air temperature really helps keep detonation away. And by the way, we made 600 horsepower with that little 355 with basically pump E85. We have other friends with turbo motors who routinely make between 700 and 800 rear-wheel horsepower using E85.

One thing we learned from Tim Wusz, who works for Rockett Racing Brand gasoline (that sells a racing E85 fuel) is that for every 25 degrees you lower the inlet air temperature, two things happen. The mixture density is greater, which adds roughly 2.5 percent power, and the fuel’s octane requirement is reduced by one full point. So starting with a fuel measuring 105 and lowering the octane requirement is the reason that E85 works so well for boosted engines.

This is a Quick Fuel E85 carburetor we’ve used on several occasions that has worked like a champ. If the carb will be stored for any length of time, it would be best to run a mixture of regular pump gasoline through the carburetor to prevent corrosion.

This is a Quick Fuel E85 carburetor we’ve used on several occasions that has worked like a champ. If the carb will be stored for any length of time, it would be best to run a mixture of regular pump gasoline through the carburetor to prevent corrosion.

Yes there are some other tuning issues you need to deal with. If running a carburetor, the best thing is to convert to an E85 carburetor. Our experience with Quick Fuel Technologies has been excellent and they have a wide selection of different carburetors designed only t use E85 fuel–and they’re green in color so you can’t miss ‘em. This is a requirement because the caloric heat available from a pound of E85 is roughly 30 percent lower than a pound of gasoline. This means you will need to flow 30 percent more fuel to make the same power. So you will burn roughly 30 percent more fuel compared to gasoline, but where else can you buy 100+ octane fuel for around $2.00-per-gallon? If you do, please let us know. You will also need stainless steel filters as there are some problems when using paper fuel filters with E85.

Another important point we learned (the hard way) is that ethanol is extremely sensitive to pre-ignition, which means even the slightest hot spot in the combustion chamber can light the fuel long before the spark plug lights, and you don’t want that to happen. In our case, it was due to a projected nose spark plug where the long ground strap became hot (making 550 horsepower at the time) and the fuel pre-ignited just as the intake valve closed. The engine immediately lost power and we discovered a dead cylinder. Usually, pre-ignition causes massive engine damage–usually to pistons. In our case, we were very lucky and it merely caved-in the intake valve, which caused it to lose its seal, which created the lost compression. We replaced the intake vale and changed to a very cold heat range, non-projected nose spark plug and the engine was very happy from then on.

I’ve tried to offer both sides of the argument to using E85, but there are hundreds, if not thousands, of enthusiasts using this fuel all the time with amazing results. I think as long as you do your maintenance properly, E85 offers some potentially very rewarding results.

And the stuff is a lot cheaper than race gas!

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  1. Troy LaCrone says:

    Jeff, this is Troy L, your old buddy. Shoot me an email please, want to re-connect with you and no longer have your cell.

  2. What is a general safe effective compression ratio on E85? The net results in varying opinions from 13:1 up to an extreme 20:1.

    • Bruce M. Guertin says:

      We’ve tested E85 to 14:1. I and a friend of mine have a lot of experience with E85. Here’s what we discovered in over 200 dyno pulls and running it in various cars. 1. It’s an inexpensive alternative to 110 octane race gas if you can get it. If you have to drive a long distance to get it, don’t. The cost benefit just isn’t there. 2. If you leave it your fuel system for 6 months like a friend of mine did I can guarantee you’ll have corrosion issues. 3. Don’t buy the high priced “race” E85. If you have to pay the price that’s asked for that stuff just run 110 octane. 5. An e85 carb conversion is something the average racer can do himself easily.

      • I have it local about 10 minutes away. Pretty convinced to use it on my SBC “baby blower” street car build. The mini blowers react very well to nitrous due to the cooling effect being so inefficient/highly overdriven. I would think E85 would be a great combo. Just trying to dial in a safe compression with about 6lbs.

  3. Russell Saunders says:

    My Dad and I have been running it for 6 years now with zero issues. 13:1 compression 454 and 540 bbc. Just fill the aluminum fuel cell full over the winter and cap off the vent. Run regular fuel through the carb. We let them sit for 4 months or so in the winter and fire them right back up in the spring. Drive them every 2 to 3 weeks. No issues at all. Just bought it for $0.96 a gallon. Usually mix an ounce of marvel mystery oil in every 5 gallons. Absolutely love this stuff!

  4. MotorCityMike says:

    Have been running E85 in my street driven, carbureted roots blown 540 big block for several now. With certain precautions during storage, there is no corrosion/oxidation issues. Absolutely LOVE this fuel. Cruise all day long in 95* heat with no problem, and click off mid 8 second passes with ease in a 3500# car using dirt cheap fuel.

  5. Pingback: Ask Away! with Jeff Smith: What is Safe Effective Compression Ratio for E85? - OnAllCylinders

  6. Going on 12 years of running E85 and E100 in my 1970 GTO, and two years in the 65 GTO. I’ve run it in my 98 Formula and a 98 Gran Prix as well. I never drain the tank, never drain the carbs, I park them in October or November, whenever the first snow arrives, and they sit until May when the salt is finally off the roads. I don’t do anything special, the 70 is running the original tank and lines under it. I have photos of Qjets I have converted five to ten years ago that show zero corrosion after sitting for months or years at a time with fuel in them. E85 evaporates from the bowls before long anyway.

    I make my own E100 and it has between 10% and 5 % water still in it, and zero issues with hydrous ethanol.

    In the later article Jeff did, it is not the ethanol causing the corrosion issues, it is the additives they put in doing the damage. Everyone blames ethanol but its not the culprit. If it was ethanol and the little bit of water still in my fuel, I would be having lots of problems after more than a decade. As it is, my tanks, lines, carbs, and pumps are all spotless and last longer than they did running pump gas in the 80s and 90s.

  7. Been running E85 for a year in a 2017equinox 4 cylinder with great performance. No additives. Live in Wisconsin. Temps 90 F in summer to -50 F in winter. My only concern is starting is delayed a few seconds. Any advice for me?


  8. I have a sbc 383 stroker in my hot rod with 13.5 to 1 compression a tunnel ram and 2 four barrel e85 quick fuel carbs. i was told that if i let it sit in the garage for 2 or 3 weeks without starting it , that i have to drain the fuel tank and carbs. and put fresh e85 in it . or the e85 would gum up the carbs. and make it run shitty. and it does run shitty. what should i do? Reddog.

    • joseph burgess says:

      I have a naturally-aspirated 2012 6.2L Flex Fuel vortec that I have run exclusively only flex fuel with 110k miles that sits outside a lot in the Northeast corridor of the U.S. I have used ethanol treatment (Lucas) for the last 6 years and have left my fuel tank under 1/4. It will start but it is not drive-able, causing me to limp dangerously to the pump. I’ve checked and changed quite a few things, but what needed changing was my attitude! Never leave your tank low without a water-preventative additive like Stabil or Lucas, and take it from me, MAKE SURE TO USE THE RIGHT AMOUNT! The old boy sits then runs like a top all seasons!

  9. Marc J Rauch says:

    There is far too much wrong information in Jeff Smith’s article. For instance, ethanol and methanol are no more corrosive to aluminum than gasoline and aromatics. Also, ethanol does not pull water out of the atmosphere, it absorbs water that it comes in direct contact with – usually from natural condensation. The same amount of water from condensation will form in a fuel tank even with ethanol-free gasoline. At least, the ethanol helps to get rid of the water.

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