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Mustang Fuel Change Up: E85

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Along with air delivery, fuel is the key to feeding your pony more power. Injectors, fuel pumps, and the like will compliment your other mods and compensate for the influx of air. The last thing you want is a too lean mix and a detonation ruining your hard work.

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Internal combustion engines, as we know, rely heavily on fuel in order to make power. There are different types of fuel that can be utilized. A growing, more common fuel, is a great alternative to traditional pump gas. E85 stands for 85% ethanol and 15% gasoline. At a normal pump gas station ethanol percentage can be up to 10% ethanol and the rest gasoline. There are many benefits, along with a few drawbacks, of running E85.

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What is the Overall Purpose of E85

It’s simply a different type of fuel, general speaking. E85 is primarily utilized when more power is desired without making any other changes (other than a tune and fuel components). It is rated at 100-105 octane and runs cooler than traditional gasoline which allows the car’s timing to be increased, making more power overall. For large, boosted applications, this can result in a solid increase in power. Another nice benefit of E85 is the price. When in comparison to traditional gasoline, it’s cheaper by the gallon, which means more rubber to lay down on the street!

2015 BAMA Tuned Mustang Burning Rubber

What are the Drawbacks of E85?

There are only a few drawbacks of using E85. The primary one is the availability: it’s not readily available all throughout the US. It’s highly suggested to check and see where the local E85 stations are, if there are any that is. The other big negative is simply it burns more fuel. E85 has a lower BTU than traditional gasoline. A BTU is a British thermal unit, which basically is how much energy is in the fuel itself. E85 has about 33% less BTUs than traditional gasoline. As a result this decreases fuel economy. While the price per gallon may be cheaper than 93 octane gasoline, you will be buying more of it at the pump. It’s best to see how often you drive, how far, etc. to determine if it is worth the potential additional fuel cost.

S550 Mustang Cruising Through Farm Country

What is Needed to Convert to E85?

The past few years of Mustangs are extremely simply to convert to E85. The only things truly required on a 5.0 (S197 and S550 models) are simply fuel injectors and an aftermarket tune. That being said, it is never a bad idea to look into an upgraded fuel pump since you will be pushing more fuel throughout the engine.

Running E85 on pre-2000s Mustangs

Running E85 seems to be a magical remedy for creating more power. The truth is that E85 isn’t some power potion that makes a car run any faster. On Foxbody Mustangs and older cars where ignition is typically run advanced and compression ratios are higher, E85 allows the car to run to its full potential. The enemy in these engines is the detonation of fuel. This means the fuel combusts prematurely and power is lost. E85 works to prevent the detonation from occurring.

To run E85, which has high ethanol content, you will need to address the fuel system. With Foxbody Mustangs, you should look toward adding a flex fuel sensor along with replacing any o-rings or seals in the system along with the fuel lines so the ethanol won’t damage them.

What are Flex Fuel Sensors and Why Do They Matter?

Flex fuel sensors are devices that are necessary for running ethanol in a vehicle. It is a device used to measure the level of ethanol in the fuel returning to the tank. The flex fuel sensor is matched with a proper ECU which can adjust timing, fuel, and boost in order to make the most power out of what ethanol is being used. E85 is a blend of fuels, gasoline and ethanol. The blend implies that at any given time, the fuel being burned can be of an uneven mixture. You can’t control how the blend cycles but you can control how the car responds. Rather than letting the engine run the fuel at a consistent rate for an uneven power output, the ECU can dial it in for a flat smooth curve in the power band.

How Much Power Can I Make from the Change?

While gains can vary from the specific modifications to one’s car, there will always be a solid power gain at all rpm levels in both horsepower and torque. In a naturally aspirated form, E85 is a great option if all other modifications have been deemed too costly for the gains. In a boosted application, the gains are much more amplified as E85 coordinates well with superchargers and turbochargers.


Key Points of E85

To summarize, E85 can be broken down into a few facts:

  • Can gain horsepower and torque all throughout the rpm range with minimal changes to the engine
  • Gains more toward boosted applications, but also great for NA
  • Higher fuel consumption, but generally cheaper to purchase per gallon in comparison to traditional gasoline
  • Tune is required for E85 with minor fuel system modifications as well
  • Higher octane than 93 octane gasoline
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