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Jul 29 2014

Auto Technology: Alternative Fuel

For many drivers, gasoline and diesel are the only forms of vehicle fuel they’re aware of. Every gas station they’ve filled up at offers multiple grades of gasoline and at least one grade of diesel. However, these are not the only options anymore. Ethanol, biodiesel and compressed natural gas are three popular alternative fuel sources we will discuss in this article.

The alternative fuels mentioned above, though still not as widespread as petroleum fuel, have started to gain more traction over recent years. For those that have read the text on a pump – aside from the rapidly scrolling numbers – you may have noticed the alcohol content label below the gasoline fuel grade, showing a small percentage of ethanol. The increase of consumer vehicle models compatible with alternative fuel has certainly contributed to the wider spread availability of these environmentally friendly fuel sources.

There tends to be a lot of confusion and questions among consumers about the different alternative fuel options available in the U.S. market. And for those of you already familiar with them, this article will identify some of the advantages and disadvantages of using these alternatives in place of petroleum based fuels.


Ethanol is a renewable fuel source produced from corn, primarily in the Midwest. It's the same alcohol you would find in a bottle of Grey Goose. As a vehicle fuel source in the U.S., ethanol is blended with gasoline at different ratios including E5, E10, E15, and E85. The number following the "E" represents the percentage of ethanol in each blend (see exception for E85 below).

Lower level blends up to E10 account for over 95% of all gas consumed in the U.S, so there's a good chance ethanol is in your car right now. Though all manufacturers approve the use of blends up to E10, E15 is currently only approved for vehicles manufactured in 2001 or later.

Use of E85, mainly in the Midwest where it's produced, requires special vehicles with flex-fuel engines. According to fueleconomy.gov, E85 blends can actually range anywhere from 51% to 83% ethanol, with lower percentages generally used in colder climates. If you’re interested in which manufacturers offer flex-fuel passenger and light-duty vehicle models, check out this list here.

Below I’ve listed some of the advantages and disadvantages of E85 in comparison to traditional gasoline.

E85 Advantages E85 Disadvantages
  • Domestically grown renewable resource, less dependency on fossil fuel sources
  • Boosts octane and reduces emissions when blended with gasoline
  • Provides more torque and horsepower resulting in better acceleration
  • 18% to 29% less MPG than pure gasoline (contains less energy)
  • Currently more expensive than gas, on a cost-per-mile basis
  • Not as readily available in regions outside of the Midwest


Flex-fuel vehicles currently don’t have many advantages over gasoline vehicles, since E85 ultimately may end up costing more and is not as readily available in the majority of the country. However, they do show promise as cleaner burning vehicles and may become wider spread if gas prices continue to rise.


biodiesel fuel technologyBiodiesel is a renewable resource produced by re-purposing cooking oils, such as vegetable oils, animal fats, and recycled cooking greases, and blending them with diesel fuel. The different blends available in the U.S. are B2, B5, B20 and B100. These numbers, similar to the numbers following the "E" in ethanol blends, represent the percentage of biofuel in the blend.

Most auto manufacturer's diesel vehicles are approved for blends up to 5 percent (B5) with some options available that are approved for blends up to 20 percent (B20). In some states, blending a small percentage of renewable biodiesel fuel into petrodiesel (generally under 5 percent) is required by law. Each vehicle model has certain blend requirements that should be checked by consumers before fueling, as too high of a blend could potentially damage the vehicle.

Another factor to consider is that highly concentrated blends are more likely to crystallize at very low temperatures. According to fueleconomy.gov, B20 blends using No. 2 diesel are manufactured to perform the best in colder climates.

Like any other fuel source, biodiesel has its pros and cons.

Advantages Disadvantages
  • Produced domestically and is a renewable resource
  • Cleaner option in diesel vehicles before 2010. (Modern clean diesel engine tech has a comparable green score)
  • B5 can be used in most diesel engines
  • Improves fuel lubricity, resulting in longer engine life
  • Currently more expensive than traditional diesel
  • Not as readily available
  • Most diesel engines not compatible with higher blends
  • Modest performance sacrificed
  • Higher blends lack in cold weather


Though biodiesel helps to cut down on diesel consumption and emissions on older diesel vehicles, it’s unlikely to fully replace diesel any time soon. In general - unless you have a deal with a couple of local fast food joints - biodiesel is more expensive than diesel (as of this writing), and is less convenient to access in blends above 5 percent.

Natural Gas

Natural gas is an abundant fossil fuel in the U.S., that once compressed (CNG), shows promise as a vehicle fuel source. Compressed natural gas - already popular with heavy-duty trucks - has just started to come around as a fueling option for consumer vehicles.

Currently the only available car in the U.S. powered by CNG is the Honda Civic. However, CNG bi-fuel options have become increasingly more available for vans and light-duty trucks. Just as it's named, these vehicles can run off of two types of fuel, either simultaneously or individually. To do so, bi-fuel vehicles require two fueling systems, one for CNG and the other for gasoline. Refueling stations for CNG vehicles are quite limited. As a result, drivers interested in a vehicle fueled on just CNG may want to factor in the installation of a small home refueling appliance as part of the cost of ownership.

Below I’ve listed some of the advantages and disadvantages to consider with CNG in comparison to gasoline.

Advantages Disadvantages
  • Plentiful resource in the U.S.
  • More environmentally friendly option
  • Less expensive
  • Same MPG
  • Home refueling capability
  • Bi-fuel vehicles can use just gas if needed
  • Not many CNG passenger vehicles currently available
  • Shorter driving range on a tank
  • Limited refueling stations
  • Less cargo space due to a large tank in the trunk
  • Consumer concerns with having a CNG tank on board


Though still in the early stages with only a few manufacturers offering vehicles equipped for it, there are several advantages that could make CNG become a more popular alternative. As of now, choosing CNG would be an investment, given that the cost of CNG models are more expensive than traditional gasoline models and equipment for refueling at home is also an additional cost. 

The Future of Alternative Fuel

There are many benefits, as well as challenges, for all three of these alternative fuel sources. As oil prices continue to rise, these domestically produced, Eco-friendly fuel options may very well gain greater use as vehicle fuels in the future. For those concerned about the lack of readily available alternative fueling stations at this point, many of these specially manufactured vehicles are able to run off of traditional petroleum fuel when needed.

As interesting as these alternative fuel options we've discussed may be, there are other more established and rapidly growing economy vehicle technologies on the market that you're most likely familiar with. In the next article of our auto tech series, we will clarify all the variations of hybrid electric vehicles as well as discuss the ins and outs of fuel cell technology.  

In the comments section below, please share with us your opinions about these alternative fuel sources and whether you could see any of them fit as viable fueling options.

Useful Resources

Check out our EPA vehicle MPG data and EPA green vehicle data infosheets if you're looking to integrate this information into your vehicle database. 

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Proceed to the next article So Many Hybrid Vehicles. Is There Really Any Difference?

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