The Big Fuel Test Part 5: E85 Versus All—The Winner is Crowned!

This article is the fifth and last of our Big Fuel Test series (Article 1: Introduction, Article 2: BOOSTane, Article 3: Meth Injection, Article 4: Race Fuels Fight Back), which spanned 13 different test fuels, octane additives and injections. During this final installment of the series, we review the ethanol-based fuels (E85, C85) and get the results of this power-making shootout, all of which was performed at The Tuning School’s facility in Odessa, Florida.

After all this testing, it was clear there would be two fuels left slugging it out for the victory. Ethanol (E85) and methanol injection were the two clear winners leading up to this pivotal point in the article series.

The results of all tests are in, so let’s get to it!

Testing in this final round were the following fuels and injections:

  • Pump E85 from a local station (40-percent as tested from the pump)
  • VP Racing’s C85 (40-percent for consistent testing and fuel system limitations as well)
  • VP Racing C85 plus meth injection (40-percent for consistent testing and fuel system limitations)
  • VP Racing C16 plus meth injection

Just to be clear: we were limited to 40-percent ethanol testing for two reasons. The first reason is simple—that’s what actually came out of the pump when we bought “E85,” which typically varies from tank to tank. This means that the concentration of ethanol was actually only 40-percent, and gasoline made up the remaining 60-percent. We would have preferred it be what it claimed (85-percent ethanol, 15-percent gasoline) but that’s what it actually was. As it turned out anyway, due to fuel system limitations, we couldn’t run any higher than 40-percent ethanol. The volume of fuel the car required exceeded our test car’s ability to provide it. So for those reasons, we didn’t increase the concentration and performed all tests at 40-percent ethanol concentration. This is a common issue with direct injected vehicles without heavy fuel system modifications.


Here are the results for the pump E85 versus 93 octane pump gas:

Pump E85 was a killer fuel after tuning, as it made a solid 618 rear-wheel horsepower on our Mustang Dynamometer, soundly defeating our baseline fuel of pump 93 octane gasoline at 574 rear-wheel horsepower. It also beat 93 octane plus meth injection (we’ll call that 93+MI) by 2 horsepower—and as you know I’m going to point out, that’s in the margin of error; which means it’s not enough to call a true winner.

That’s right, if you recall from article #3 of this series, our 93+MI runs resulted in a roller spin measured at 616 rwhp.

Let’s take a moment to let the internet burn to the ground. That’s the end result??? The power output of pump fuel plus meth injection against E85 showed virtually the same result? I can only imagine the flame wars brewing in the interwebs! We just started automotive World War III, so to speak.

Not happy with leaving this alone—having a shared winner for our series—we performed several more tests to help us declare a final winner. With pump E85 now sharing the winner’s crown with 93+MI in a tie for the victory of the entire test series, we thought maybe VP Racing’s C85 could be a clear victor. So we drained the pump E85 out and filled up with C85.

As we hoped, the race fuel came through and made a show of its strengths. Check out the results below. 93+MI results are the solid lines, and dashes are VP Racing’s C85.

Now with a clear victory in hand, we should have stopped. 629 rwhp was clearly the best result to date, and made a solid case for VP Racing C85’s superiority over 93+MI… the debates began among our own staff. We knew the cries of the meth injection junkies would be coming in fast and furious upon reading these results; how we needed a race fuel version of E85 to beat meth injection and lowly pump gas… How it wasn’t really pump E85 that won. VP Racing’s C85 won: the pure race version was needed to make it the winner. What could we do?

So, we ran two more tests—and the surprises kept on coming. The roller coaster had two more twists before we were able to close out this series and call a real winner.

In order to be fair, we decided to give the meth injection camp another chance to win, by running the best non-ethanol fuel we had tested (VP Racing’s C16) with meth injection on top. Surely this would bring the meth injection camp the glory we know they seek. Sadly for them, the car made less power with C16 plus meth injection than it did with 93+MI. We were able to make only 605 rwhp after exhaustive testing. We had suspected this could happen, with too much octane creating such a slow burn that we simply couldn’t make the power we hoped for.

So, as we said earlier, we had a clear victor and should have stopped. But we took a request from the meth injection camp for one last and final test. What if we tested VP Racing’s C85 plus meth injection?

What if we combined both for one last test, just to see? That’s where the internet begins to burn down again. Behold, the Final Test Results and the winning fuel combination of the entire series:

Making 632 rear-wheel horsepower and 558 lb-ft of torque, the winner of our series is… the combination of VP Racing C85 with meth injection!

Again, we’re left with one inescapable conclusion—E85 and meth injection are both amazing options and both are better than pump gas alone. They fight for each last horsepower and came out virtually identical in all our testing, and when combined together, they worked even better. Maybe that will help quench the internet fire over the superior solution. Maybe it will just generate more chatter. Who knows—but it’s up to you, the reader, tuner, engine builder, whomever is reading this, to look at the charts and determine what’s best for your actual combination.

To help with that, here’s some more data.

Here’s our final results chart, with all fuels, octane enhancers and injections we tested:


Below is a chart showing percentage gains:

The 5-10-percent gains you see above (30-60 rwhp gains) using just different fuels are very impressive. When you understand that a decent camshaft upgrade on an LS/LT Engine will also net 5- to 10-percent gains (30-60 rwhp gains) over a stock camshaft, you can see how important it is to choose and tune the correct fuel for your application!

There is one more way to look at these results. You can look at these from a perspective of dollars versus improvements. In the chart above, we can look at the results from 93 and BOOSTane (4.2-percent) to VP Racing’s C16 (5.4-percent) and see a trend. You can get about 5-percent more power than pump gas for a small upfront investment. That means, you can simply add BOOSTane into the tank, or any of those race fuels and with the right tuning, gain about 5-percent power over 93 octane pump fuel; about 30 rwhp in our example.

However, in the chart above, it looks like once you start getting about 6-percent gains and higher the costs go up pretty quickly. Looking from 93 plus Boost Juice (5.9-percent) and higher gains, the up front costs go up at least $500 due to the parts needed for a good meth injection kit. Assuming you’re going to inject methanol, you’ll need a good kit of about $500-$750.

Assuming you’re going to run one of the ethanol-based fuels, you’ll need larger injectors ($500-$1,000) and potentially more fuel system components (another $500-$1,000). So, depending on your budget, you can have roughly 5-percent more power for very little cost up front, or 6- to 10-percent more power with a bit more money outlay ($500-$2,000 for fuel system upgrades).

E85 Pros

  • Made the highest power of all testing we performed, including the best race fuels
  • Ongoing costs of operation are very low compared to race fuels
  • Average cost per gallon comparable to pump gas
  • Easily available in many states
  • Well supported and commonly used in the aftermarket performance industry

E85 Cons

  • Up front costs to set up your vehicle to run it can be high (injectors, fuel pump, lines, etc.)
  • Quality and concentration can vary from pump to pump (E85 may not always be 85-percent Ethanol)
  • Quality and concentration can vary from season to season (winter blend is different than summer)
  • Cold starts can be difficult
  • Tuning make take more time and cost, but most can be automated to adjust for changes in fuel quality

Tuning Notes:

Ethanol-based fuels are not something we recommend a beginner tuner attempt to work with. To do a good job and not wash down the cylinders, the tuner should be able to tune the combo in question on pump gas in his sleep. In relation to that, we always recommend you finish tuning the vehicle on pump gas first before going and switching to an ethanol-based fuel. We do this for a few reasons, the first being most tuners can easily recognize issues with the tune when working with pump gas. They can easily spot a mechanical problem and not mistakenly cover it up with tuning changes. Second, it allows you to show a baseline pull or pulls, with power progressing as you make spark changes, until you finish and find the best possible power on pump gas. After that, you can change out the fuel for an ethanol-based fuel, retune and know for sure what kind of gains really came from changing fuels.

The ethanol-based fuels are also best tuned using Lambda method instead of air/fuel ratio due to changing stoichiometric ratios from the changes in fuel quality. For example, filling up with “E85” that turned out to be only 43-percent ethanol, would have a stoichiometric value of 12.18:1, but E85 has a stoichiometric value of 9.77:1. Due to the fact that these are constantly changing from fill up to fill up, it’s easier to tune using Lamba—because Lambda never changes. If you aren’t familiar with how this works, have a look at the table below, taken from The Tuning School’s GM Advanced Level 2 course.

In this case, VP Racing’s C85 preferred Lambda of .85-.87, while pump “E85” preferred .82-.84, a bit richer. Look at the chart above to equate that to gasoline AFR, if you are used to working or thinking like that.

VP Racing’s C85 also preferred 23 degrees of spark advance, while “E85” preferred 22-23.

Tuning for wide open throttle is simple, once you get the correct Flex Fuel tuning set up with a good Ethanol content sensor. Without such a sensor, you are constantly monitoring the Ethanol content of each fillup, and then manually changing the Stoichiometric value in the tune, which is a real pain and reiterates the need for a quality Flex Fuel tune. Another aspect of the tuning process with ethanol-based fuels to keep in mind is your wideband sensor and gauge. If your wideband reads in AFR, then you will see the same AFR you are used to working with during gasoline based tuning, unless it has an option to change it to know what fuel it is working with, and you have changed it to know it’s working with ethanol. If your wideband reads in Lambda, then it will not be affected—which is another reason to tune using Lambda when working with any ethanol-based fuels.

One last component to this evaluation is the human factor. We decided to ask a few industry expert friends and a few who work with us. We asked if they preferred meth injection or E85, and why.

Ron Mowen, owner of Vengeance Racing, said: “I think they both will ultimately make similar power, but E85 is much safer in the long run if you can justify the fuel system costs associated with it.” Vengeance Racing is known for building some of the nation’s fastest LS/LT powered vehicles, including road race and airstrip attack cars.

Tony Gonyon, owner of Tuners Inc. and also The Tuning School’s Ford course instructor, said he “prefers E85 if they have the proper supporting mods, if not then meth injection is fine.” Tuners Inc. is known as one of the premier tuning shops in the nation.

Stephen Taylor from VCM Performance in Melbourne, Australia noted that E85 is far more popular in Australia’s performance market.

Brett McClelland, one of our instructors at The Tuning School, noted that E85 is most popular among the students they teach.

Our other instructor, Josh Hofstra, noted that E85 is great for knock control in high-horsepower builds (1,000-plus) from experience, and meth injection can also be great.

My personal opinion is that the correct answer depends on the engine and build you have, who the customer really is, and how much budget can be put into the vehicle. If you can commit to the money needed for an ethanol-based solution, you have good ethanol-based fuel readily available in your area, and you are going to have a proper Flex Fuel tune done, then you have a great option for maximum power. However, I still prefer meth injection for most solutions, due to ease of installation and history of performance, as I have used this solution personally and professionally since 2003 with success.

I have seen too much variance in ethanol’s performance to consider it any type of reliable replacement for a race fuel in a high-dollar build. I do believe race fuels are still best when you aren’t building on a tiny budget, and you have a lot of money in the engine that could be saved with a quality fuel. If ethanol is still your hangup, they make C85 for that: a known-quality ethanol-based race fuel I can live with on the expensive builds.

Tuning Results & Fuel Evaluation:

Testing and tuning of the ethanol-based fuels was as difficult as doing the meth injection tuning. If you or your tuner isn’t familiar with tuning either E85 or meth injection, you’re in for a long day on the dyno. Just like tuning meth injection, ethanol or E85 is fuel you are introducing into the combustion process. Unlike gasoline, it burns differently and at different rates. The quantities needed are different: more E85 is needed than gasoline, typically 20- to 35-percent more. E85 is the designation for an ethanol-blended fuel where ethanol makes up 85-percent of the content, and gasoline 15-percent.

E85 has a few issues you need to take into account before using it.

Understanding why E85 makes better power than pump gas is important. Depending on who you ask, your answers will vary – but we have a few of those reasons from our conversation with Freddy Turza, Technical Manager at VP Racing. One of those reasons worth mentioning that you probably haven’t already heard is called Hydrodynamic Pressure. This term means that due to the extreme rich mixture required of E85 to produce power, a byproduct is extra compression from the space taken up by the fuel in the combustion chamber. Extra compression creates extra power, plain and simple. However, Freddy noted that the E85 craze is subject to poor quality from pump to pump or time to time.

From our perspective, this makes it even more important that your tuner perform a good flex-fuel tune so the ECM can recognize the ethanol content as the fuel flows into the engine from the tank. This means your tune will automatically adjust the Stoichiometric air/fuel ratio and spark settings as required by the changing ethanol content from pump to pump.

The final evaluation of what fuel is right for you rests in your hands. In summary, you can gain about 5-percent more power than high-octane pump gas for very little investment because of great products like BOOSTane, and VP Racing’s MS103 or MS109. Just drop it in the tank, tune it and roll. When you want 6- to 10-percent more power is where the questions begin to arise, and the winning combination of fuel plus meth injection or E85/C85 will be entirely up to you to evaluate. I’d suggest keeping an open mind for your combination, and to even test and see what benefits your combination best.

Remember this – to be the winning racer doesn’t necessarily mean you have the newest and best stuff. Sometimes the winner is the one with the most time testing and experience to really dial in their combo, making the most power possible from the build, right down to knowing the best possible fuel. Thanks for reading our series, and stay tuned for our next series – where we test injections like you’ve never seen or heard of before.

Article Sources

About the author

Bob Morreale

Bob Morreale is the author of several tuning related books and courses for The Tuning School. Bob began programming using BASIC in the mid-'80s in 2nd grade; and progressed to other languages, including HEX, self-taught. While Bob can program, he prefers to do tuning related R&D on new vehicles, writing courses and then teaching the tuning process. Bob has over 18 years of tuning experience, starting with the legendary turbocharged 1987 Buick Grand Nationals to modern LS/LT and Ford powered vehicles. Bob has also written numerous technical articles for industry-standard magazines and conducts “Tech Tuesday” video interviews for The Tuning School. Bob enjoys road-racing and drag racing.
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