What Is E85 Gas and Should You Use It?

by Andy Jensen (Advanced Auto Parts) ... E85 is widely available, an affordable alternative for many popular vehicles. Here's why you should take another look at ethanol. ... E85 is a gasoline and ethanol blend, much like your regular gas. If you fill up on regular 87 octane, the ethanol/gas mix is probably 10% ethanol and 90% gasoline, labeled on the pump as E10, or possibly “with up to 10% ethanol." After leaded gas was phased out in the 1970s and '80s, manufacturers looked to oxygenates like methyl tert-butyl ether to increase gasoline octane while reducing emissions. After finding poisonous MTBE in groundwater, manufacturers moved to the much safer ethanol additive in the early 2000s. Depending on where you live, regular gas could have no ethanol content or be as high as E30, which is 30 percent ethanol, 70 percent gasoline.

“Ethanol is a domestically sourced, low cost, cleaner-burning, octane-enhancing fuel additive," said Robert White, Vice President of Industry Relations at the Renewable Fuels Association. “The higher the octane gets at the refinery, the more expensive it gets. That's why premium is more expensive than regular 87 octane. When you use ethanol's octane to finish those gallons, it saves a lot of money for the consumer."

E85 is dramatically cheaper because most of the ethanol in North America is processed from corn. This yellow field corn is indigestible by humans and is grown either as livestock feed or specifically for ethanol production. Since the growth, production, distillation, and shipping are all regionally local, E85 tends to be cheaper than even the most sketchy gas station's cheapest regular fuel, and dramatically cheaper than premium 91+ octane blends. This seems like a deal, especially when looking at the octane rating.

Have a look at your owner's manual. If your vehicle is flex-fuel capable, then all you need to do is fill up with E85 instead of gas. Look for the yellow pump handle (or the dramatically lower price) and fill until you hear the pump shut off. Be sure to get your gas cap tight. On restart, the vehicle's sensors will automatically detect the ethanol content, and adjust engine settings to compensate.

Let's say you don't own a flex-fuel vehicle, but you're interested in E85 anyway. You still have options. Some modern vehicles just need a computer retune and the addition of a flex-fuel sensor, and they are effectively the same thing as a factory-installed E85 option.

If your vehicle is new, you probably want to know if E85 voids your warranty. In a flex-fuel vehicle, the easy answer is no. Drive off the lot, fill up with E85 in your brand new ride and you still have 100% of your warranty in effect. If you have a non-flex-fuel vehicle, however, tuning for E85 and filling the tank could void your powertrain warranty.

Now let's assume you have a Radwood-era classic that you want to upgrade. Older vehicles weren't designed for ethanol in the gas, so running high ethanol content will cause some issues. Here's what will need upgrading:

A classic EFI vehicle, like a C4 Corvette or Fox-body Mustang will need more than just the computer tune and ethanol sensor. Since ethanol has lower BTUs, you need to increase the flow rate to let the engine burn it properly. Otherwise, you will run lean. Expect to swap out fuel injectors and likely the fuel pump. These stock units weren't great anyway, so expect to see a performance gain just with modern stock replacements. Look for parts that are E85 approved, and if you have any doubts, contact the manufacturer.

For a truly classic vehicle, such as a Chevy Corvair or Plymouth Barracuda, you will likely be replacing the entire fuel system front to back.

A Scion FR-S isn't exactly the fastest car available (or even in its class) and during a cold air intake test, this one (pre-intake) put down 160 horsepower and 142 lb-ft at the wheels on 93 octane ethanol-free gas. With the Scion returned to factory stock form, but running an E85 tune and a tank full of corn from a local chain gas station, we returned to Abel Racing for another dyno to see how much power it had picked up from this one change.

A summer dyno test fielded hotter and more humid weather, but the car still put down 175 horsepower, and the same 142 lb-ft [sad trombone noise] at 7,000 RPM. However, low-end torque saw noticeable gains, with a 22 lb-ft increase at a more real-world 4,000 RPM. Gas mileage fell, averaging 26.2 MPG over two tanks, approximately a 20% decrease but that was with several on-ramp tests. A more conservative driving style shouldn't take that much of a hit. Despite the mileage decrease, the benefits easily outweigh the negatives and this car will likely stay on E85 for the rest of its on-road life. READ MORE