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E85 vs. Gasoline Comparison Test

Running on Alcohol Fumes

This article compares the costs, performance and efficiency of gasoline and ethanol. Together with other articles published as part of Edmunds' ongoing coverage of alternative fuels and advanced technology, this piece will help consumers understand the costs and benefits — both financial and environmental — of the choices becoming available to them. See also "Fueling Up With Ethanol" and the Fuel Economy Center.

As our government and U.S. automakers increasingly push us toward an ethanol solution to our energy problems, we decided to pit gasoline against ethanol in a comparison test. What kind of fuel economy will you really get using E85 (85 percent ethanol, 15 percent gasoline)? How far could you go on a tank of ethanol gas? And, for motorists tired of high gas prices, will ethanol-gas really save money? Is there a significant difference in greenhouse gas (carbon dioxide) emissions?

We drove a 2007 Chevrolet Tahoe from San Diego to Las Vegas and back on gas and then on E85 ethanol to compare fuel economy.

We drove a 2007 Chevrolet Tahoe from San Diego to Las Vegas and back on gas and then on E85 ethanol to compare fuel economy.

In short, should America bet the farm on ethanol? Or are there unforeseen problems with this "flex fuel"? We thought a long-distance road trip from San Diego to Las Vegas and back would reveal if this highly touted corn-based fuel is a long shot or a sure bet.

Using a flex-fuel vehicle, a 2007 Chevrolet Tahoe LT from our long-term fleet, we planned our test around what then was the only currently available source of E85 ethanol open to the public in all of California, Pearson Fuels in San Diego. Rather than drive loops around the city, we decided to turn the test into a 667-mile round trip between San Diego and Las Vegas, which was then the next closest E85 source.

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How the Test Was Run

The drive from San Diego to Las Vegas (a popular destination for many Southern Californians) was just over 333 miles one-way — within easy reach for the Tahoe running on gasoline with its 24-gallon tank. We would drive there and back on gasoline, then repeat the journey the next day on E85. In each case we'd start and end the test at the same pump to counteract pump shut-off discrepancies.

Our preliminary E85 fuel economy estimates came out 20 to 25 percent lower than the Tahoe's 15 mpg city/21 mpg highway rating on gasoline. Reaching Las Vegas on a single tank of ethanol looked doubtful. To avoid being stranded in the desert, we brought along 6 gallons of ethanol in plastic gas cans.

One difficulty was making sure we could test E85 undiluted by any residual gasoline left in the tank. To do this we would have to completely drain our Chevrolet SUV's tank before refilling with ethanol. Mike Lewis, the general manager of Pearson Fuels, arranged a mechanic to help us with that task. Pearson Fuels has a futuristic alternative fuels island that sells a number of renewable fuels.

We took along our VBox GPS data-logger, a satellite-based instrument for accurately measuring speed and distance. On a pair of steep grades we would test passing acceleration from 50 to 70 mph. Later, we would find an unobstructed frontage road and measure 0-60 mph and quarter-mile acceleration.

Run No. 1: Gasoline

At 6:30 on Thursday morning, we set out from Pearson Fuels and headed north on Interstate 15 with a full tank of gasoline. Whenever possible we set our cruise control at 75 mph, slightly slower than the flow of traffic. About an hour later, in the Riverside, California, area, we hit heavy commuter traffic and had to reduce our speed and endure a bit of slow-and-go traffic for a few miles.

Besides the performance testing, the drive to Las Vegas was, well, long and boring. Motorists sped past with expressions of eager expectation, heading for the glitz of Las Vegas with its dazzling shows and high-risk casino tables. Using GPS navigation, we headed for Flamingo Stop at 8615 W. Flamingo Road in Las Vegas. We arrived, filled the fuel tank with more gasoline, and ate lunch on the fly as we headed back to San Diego.

Switching to Ethanol

We arrived back in San Diego at 5:15 p.m. and refilled our tank with gasoline to measure how much fuel we had burned. Service Manager Jeanette Ramos was waiting with the mechanic who had stayed late to assist us. In the garage at Kearny Pearson Kia, service technician Corey Gonzales put the Tahoe on a lift, disconnected the fuel hose and siphoned out the gas. As the tank got low and the siphon slowed to a trickle, Gonzales tilted the Tahoe to drain even more gas out of the tank, leaving just enough fuel to drive to the E85 pumps a hundred yards away. That night we drove around San Diego with a full tank of E85 to dilute the trace amount of remnant gasoline.

Run No. 2: E85

The next morning, we topped off with E85 before another 6:30 a.m. departure to Las Vegas. Commuter traffic was a little faster, a phenomenon locally referred to as "Friday Light." This might have tilted the test very slightly in favor of E85 since highway mileage is better than stop-and-go traffic. However, over the course of a 667-mile trip, the difference would average out.

Along the road to Las Vegas we used the VBox to measure 50-70 mph and standing-start acceleration. Since there was a strong tailwind this time, we made an additional acceleration run in the opposite direction to calculate a two-way average and cancel out wind effects.

Approaching Las Vegas, the fuel gauge was getting very low. With the Flamingo Stop pumps in sight, the low-fuel warning light came on. This didn't happen with gasoline, so we knew we'd gotten lower fuel economy. Still, we had made it all the way on one tank of E85. Had the tailwind made it possible? We would find out on the return trip.

Filling Up With E85 in Las Vegas

The Flamingo Stop fuel station offered E85 out of the same nozzle from which gasoline is dispensed. We wondered if unsuspecting motorists had accidentally refueled with E85, intending to get gas. Unlike the diesel nozzle, which is a different size to prevent just such mishaps, the gas/E85 nozzle was one and the same.

Nearby, a man was pumping E85 into a brand-new Chevrolet Avalanche, complete with flex-fuel vehicle badges. It was a good opportunity to get some man-on-the-street reactions.

Edmunds: How do you like running on E85?

Avalanche Owner: The mileage sucks. On gas I can get 18 (miles per gallon). On E85 I get like 12.

Did you buy this truck so you could run on ethanol?


But you get worse gas mileage. So why do you do it?

To help the environment.

Footnote: This man didn't seem to fit the profile of an environmentalist, tree-hugger or greenie. He was just a regular guy trying to do something good for the planet. We experienced a small burst of patriotic pride.

Run No. 2: Las Vegas to San Diego

On the way back we were hit smack in the face (or fascia) with high winds. The same winds that had improved our fuel economy on the leg from San Diego were about to even things out on the way back.

The drive back was filled with gauge-watching. Would we make it on one tank? The headwind was clearly taking its toll. Nearing San Diego, the navigation system's "Distance Remaining" total exceeded the digital fuel range on our instrument cluster. With 55 miles to go, the low-fuel warning lamp came on. At 36 miles, we pulled over and added 5 gallons of E85, reminding ourselves to add that amount to the total when we refilled.

The Final Score: Fuel Economy and Cost

After refueling we put the fuel amounts and the prices paid into a spreadsheet and compiled a clear, side-by-side comparison for both fuel consumption and cost. Remember, these results apply only to this vehicle and to the prices in effect during our 667-mile test.

Gas Result:

From San Diego to Las Vegas and back, we used 36.5 gallons of regular gasoline and achieved an average fuel economy of 18.3 mpg.

Gas Cost:

We spent $124.66 for gasoline for the trip. The average pump price was $3.42 per gallon.

E85 Result:

From San Diego to Las Vegas and back we used 50 gallons of E85 and achieved an average fuel economy of 13.5 mpg.

E85 Cost:

We spent $154.29 on ethanol for the trip. The average pump price was $3.09 per gallon.

Gas vs. E85 difference:

The fuel economy of our Tahoe on E85 under these conditions was 26.5 percent worse than it was on gas.

A motorist filling up and comparing the prices of regular gas and E85 might see the price advantage of ethanol (in our case 33 cents, or 9.7 percent, less) as a bargain. However, since fuel economy is significantly reduced, the net effect is that a person choosing to run a flex-fuel vehicle on E85 on a trip like ours will spend 22.8 percent more to drive the same distance. For us, the E85 trip was about $30 more expensive — about 22.9 cents per mile on E85 versus 18.7 cents per mile with gasoline.

The Final Score Card: Performance

We were also interested to see if there was a clear difference in performance. Here, the news was better for the renewable fuel. While the test times were generally slower for E85, the difference was small enough to go unnoticed by most drivers. Despite the flex fuel's higher octane rating (103 in this case), the flex-fuel nature of the Tahoe's 5.3-liter V8 engine prevents it from taking full advantage.

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1/4 mile
50-70 passing, uphill (sec.)
time (sec.)
time @ (sec.)
speed (mph)
Cajon Pass
Baker Grade

* delayed kickdown

Environmental Comparison

E85 is often heralded as a way to reduce air pollution. Since increasing concerns about global warming have focused attention on greenhouse gases, we decided to track our carbon emissions during this test.

By relating our observed fuel economy to CO2 emission figures found in the EPA's Green Vehicle Guide, we determined that our gasoline round trip produced 706.5 pounds of carbon dioxide. On ethanol, the CO2 emissions came to 703.1 pounds. The difference came out in E85's favor, but only by a scant 0.5 percent. Call it a tie. This is certainly not the reduction in greenhouse gas emissions we had been led to expect.

Related Questions About E85

Recent concerns have surfaced about the efficiency of ethanol production. Some critics have actually said that it is a "negative energy source," meaning that more energy is required to produce ethanol than it delivers as a fuel. Further doubts have surfaced about the true environmental benefits of ethanol and E85. And some critics have cited the possibility of food shortages as farmers switch from growing corn for food production to growing it for ethanol. Higher corn prices have already been reported.

But our test wasn't designed to answer those questions. What we can say is that motorists feeling strapped because of current gasoline prices won't get any relief by switching to ethanol. There are sure to be some who elect to pay the premium to run on E85 to support U.S. energy independence, which is a noble act.

Looking into the future, E85 prices will almost certainly fall as production rises. But will they fall enough to offset the reduced fuel economy? And when will there be enough pumps to make it practical? A search of the federal government's alternative fuels finder shows that in 2014 there were 2,386 stations in the U.S. selling E85, most of them in the Midwestern Corn Belt states. If an E85 pump is just 10 miles out of the way, thus requiring a 20-mile round trip, you're looking at a $4 or $5 premium just to get to the fuel. We had to go 130 miles to find the only E85 station in our state at the time of the test. Eight years later in 2014, California had only 74 E85 stations, mainly in Southern California and the San Francisco Bay area. In addition, we can imagine a scenario in which elevated E85 demand will not only put upward pressure on E85 prices but may also tempt oil companies to cut gasoline prices to compete — ultimately driving the public back to fossil fuels.

We applaud the pursuit of energy independence, but is E85 the panacea promoters say it is? While it could be a part of a solution, it is clearly not a silver bullet.