Your Car on E-85: A Comprehensive Guide

A Beautiful Sight: E-85 At the Pump

E-85 is cheaper than gasoline, and allows the engine to run cooler and under less stress while making more power. In this article, I'll go over a brief history of E-85, describe what it is, and explain the pros and cons to help you decide if it's a possible solution for you. Obviously this site is based around the Acura RSX, and I've included vehicle-specific information about it, but most of this applies to all cars.

History

In the early 1990's in America, we had (and still have) an abundance of corn fields, and the government was seeking a way to rely less on foreign oil. Combining 85% ethanol with 15% gasoline, this newly popular fuel produced less greenhouse gases and met the government's needs. To further promote this new fuel, they provided tax benefits to car manufacturers that built vehicles that could run on E-85. Cars needed some specific hardware to make them run well on the new fuel:

30-50% better flowing fuel pump
30-50% better flowing injectors
Ethanol-compatible fuel line and rail
Flex Fuel (ethanol content) sensor
ECU programmed to take advantage of E-85

Once properly equipped from the factory, cars such as the Chevrolet HHR could easily injest E-85, 87 octane, or even a mix of the two. The ECU coupled with the Flex Fuel sensor adjusts the engine's operating parameters on demand to compensate for the respective fuel blend, seamlessly.

Pros

As of writing this post, 87 octane costs $3.20/Gal, and E-85 costs $2.70/Gal. The price savings can be a definite benefit of E-85. The benefits don't end with the price though; E-85 is less energy dense than regular gas, and harder to combust. While these sound more like cons than pros, this is the reason E-85 is often called "budget race fuel".

E-85's lack of motivation to combust means that it is incredibly knock-inhibitive. Since it's less energy dense, there's a much higher amount of fuel being sprayed. Both of these properties cool the cylinder to avoid early ignition associated with knock. This makes E-85 a wonderful candidate for high-strung high-compression naturally aspirated engines, turbo engines, and supercharged engines. It allows your tuner to push the engine harder beyond what it could do on regular fuel. Rule of thumb states most naturally aspirated cars will see gains of +5-10% WHP just from switching to E-85.

Below are Acura's recommendations for fueling the engines found in the various models of RSX; compression ratio is denoted by "CR", and its relevance to the required fuel octane will be explained.

K20A3 (RSX Base '02 - '06) 87 Octane or higher 9.7:1 CR
K20A2 (RSX Type S '02 - '04) 91 Octane or higher 11.0:1 CR
K20Z1 (RSX Type S '05 - '06) 91 Octane or higher 11.0:1 CR
K20A (DC5 Integra Type R) 93 Octane or higher 11.5:1 CR

This suggestion for fuel is made based on the design of the engine. 87 octane fuel is easy to ignite. 91 octane is a little bit harder, and 93 octane is even harder. Putting higher octane fuel in an engine designed for lower octane fuel generally wont hurt anything except your wallet. However, putting lower octane fuel in an engine that requires higher octane will introduce damage.

The rationale for higher octane fuel is that engines with higher compression ratios need a fuel that won't detonate until the spark plug ignites it. This is also true for engines that have had their timing advanced to make more power, and engines that use turbos or superchargers. All of these engine designs require avoidance of early detonation to prevent damage to the engine, which car enthusiasts know as "knock". Octane is just a measure of how resistant the fuel is to knock. E-85 is equivalent to 100-105 octane, but some blends will measure even higher.

A final unintended benefit is that E-85 (being that it is an alcohol) cleans your entire fuel system from top to bottom as it circulates. It's known for cleaning fuel filters and making pistons shiny, knocking off tough carbon deposits. The examples below speak for themselves.

Piston on 93 Octane Fuel

The Same Piston After 3000 Miles of E-85

Cons

There are some downsides to burning E-85 in your vehicle, however. I feel they're not damaging enough to merit not using it, but they must be accounted for.

E-85 is actually a bit of a misnomer. The United States has a spread of climates across her states, and as a result, varied blends of gas are needed to suit the conditions due to ethanol's reluctance to combust. During the summer, and in hotter states, the blend includes about 70-85% ethanol. During winter, and in colder states, the blend drops the ethanol content to between 50-65% ethanol. The lower ethanol concentration, and thus higher gasoline content makes starting your car easier in the cold.

Map of E-85 Stations in the US, Courtesy of the AFDC

Gas stations that carry E-85 can be easy or very difficult to find depending on where you live. For me, I'm about 20 minutes from my closest E-85 station, so I cope by bringing 2 5-gallon gas tanks, and fill them up when I fill my car up to reduce driving out of my normal commute too far. Luckily, finding stations that carry E-85 is a simple search away. I check by entering the zipcode of my location into the Alternative Fuel Data Center website, and you should too before you look into converting your car to run E-85. However, even if there is a long distance from the gas station, I do have a solution for you:

Sceptre Portable 14-Gallon Gas Pump

I get tired of holding my gas cans for 3-4 minutes while I empty them, and the no-spill nozzles somehow make me spill more. This one holds 14 gallons of E-85 and takes up less space in my garage. It also has a hand pump, so it doesn't have to be held up above the car. I normally wouldn't put a product showcase in my informative articles like this, but it's a game changer if you live further away from E-85 stations. It's a little expensive, but it frees up room in your garage and saves you trips back and forth to the gas station. Here's a link to pick one up. I get a small commission from your purchase and anything else you have in your cart, so you're supporting me writing pieces like this, and buying a product that will pay for itself.

E-85 is about 35% less "energy dense" than the gasoline you normally fill up your car with. What results is a cascading effect: your car will burn more E-85 to produce the same power as it did with gasoline. More trips to the gas station ensue with the decreased mileage you can travel on a full tank. This is what drives (no pun intended) the need for an ethanol-compatible fuel pump and injectors that can keep up with the increased fuel flow on E-85.

When I say "ethanol compatible", it's important to disclose exactly what I mean. Ethanol, or "ethyl alcohol" is the same as what you drink (responsibly) in the form of beer and wine. Alcohol has a drying effect that causes it to be unfriendly with rubber; this includes hoses, seals, and gaskets. All typical rubber materials have to be replaced with other materials that don't shrivel up and crack due to exposure to E-85. CPE, or Chlorinated Polyethylene is permeable by ethanol vapors, and NBR, or Nitrile Butadiene Rubber will dry out, making them both bad choices for E-85. The best choice is usually PTFE, or "Teflon" lines.

This, and Similar Badges Indicate the Car's Ability to Drink Ethanol and the Presence of a Flex Fuel Sensor

Finally, a last point on E-85 negatively is its hygroscopic property. E-85 absorbs moisture from the air, and over time can evaporate leaving that moisture behind. This can be corrosive, or just make it hard or impossible to start your car until you empty the gas tank. It can also affect octane rating. In the short term, E-85 is fine, but if stored incorrectly or kept over a period of months in your gas tank, it might be a good idea to run a tank of 93 octane gasoline through the car before storing it to prevent any issues.

A Word on Oil Choice with E-85

We talked earlier about how more E-85 needs to be injected into the cylinder to create the same horsepower as regular fuel. The additional "washing" of the cylinder bore might wash off some of the oil in the process, that coats the walls of the cylinder to protect it. There are a few opinions about it depending on what you're going to do with your car.

This is a treasure trove of information about oil in E-85 fueled vehicles. A 2017 study I found in the Royal Society of Chemistry really takes a deep dive on the topic. I'll spare you the high-science in favor of the main points.

Bio-ethanol fuels show decreased oil viscocity
Bio-ethanol fuels are more reactive, and when mixed with oil, become more acidic, speeding oil degradation and oxidation
Bio-ethanol has a higher evaporation point than gasoline, and is more likely to enter the oil sump than gasoline
Adding 6% bioethanol-gasoline blends to 94% full synthetic oil decreased viscosity of fresh oil about 30%
Ethanol rapidly and fully evaporated from the oil at 75 degrees Celcius, or 167 degrees Fahrenheit (most stock Acura RSX's reach oil temps of about 210 - 225 degree Fahrenheit under normal daily driving)
Final results show a specially formulated oil should be used to deal with the high acidity related corrosion.

According to Greg Acosta from Engine Labs, in a purpose-built drag car that is trailered to the strip and back home (like the one from their BlownZ06 team), the engine doesn't have enough runtime being run 1/4 mile at a time to boil the E-85 and water out of the oil. The oil isn't getting worn out as much as it is contaminated. Some drag guys bring their oil home and boil it in a crock pot to get the fuel out and run it again.

Now that we know E-85 does degrade oil through dilution even in fairly minimal amounts, what oil does that indicate we should use? Luckily, the American Petroleum Institute (API) and the International Lubricant Specification Advisory Committee (ILSAC) have some guidance. Here are the labels you should look for on your oil:

API SN Resource Conserving

Introduced in 2010, this formulation is safe for ethanol content up to 85% found in E-85, and are good in turbocharged and other high heat systems

ILSAC GF-5

The same as API SN Resource Conserving

These are pretty common as of writing this article, but you need to make sure you only use full-synthetic oil. Acura recommends 5 quarts of 5W-30, and an oil level check every 2 trips to the gas pump (VTEC burns some oil). Don't agonize over brands too much, what's important is the certifications and the proper viscosity. You can try different brands to see how it changes how much oil the engine burns, as is a reality of owning an Acura RSX.

If you want an easy choice, feel free to pick any of these oils that I've used.

Amsoil's Marketing Claims More Acid Neutralizing Power - A Necessary Component When Using E-85, But it Comes At Higher Cost

E-85 in the Acura RSX

I guess since this is an RSX website I should speak about your options to convert the RSX specifically to run E-85. I have a complete "how-to" article coming out detailing the exact things you need to do and buy to make it happen. Options for converting your RSX to run E-85 are as follows.

$150 + Tune DIY E-85 Conversion - The cheapest and best way to do it. This is what I did, and what I suggest you do.
$300 + Tune Sirimoto E-85 Conversion Kit - I haven't used this kit, but I've seen it installed and it's a quality kit that has everything thought out for you already. No shame in getting everything in one package, but you pay for it of course.
$210-345 + Tune SFP RSX Flex Fuel Kit - I also haven't used this kit, but it looks really OEM. They're made to order so there's a 2-4 week wait.

All of these solutions will make the same amount of power, it's really just a question of how much money you want to save. However, for higher horsepower builds over 400HP, a DIY solution is basically required to add a return fuel line. Even the kit options require some DIY modifications to the fuel sender unit, but I'll get more into that in my how-to article.

In Conclusion

With my returnless setup, I made 240 WHP, while on 93 octane I made 220 WHP. While not a huge jump in power, the combined effect of it running cleaner, being cheaper, and the additional power makes it my choice. As I build up towards the possibility of forced induction in my RSX, the power increase from the knock inhibitive characteristics of E-85 will allow a much greater jump in horsepower than normal gasoline. Altogether, I'm fairly happy with my transition to this more environmentally-friendly fuel, and hope to see it in more gas stations in the future. Thank you for reading, and I hope you learned something.

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