Which Gas to Choose for Your Car?

With high fuel prices these days, it's not surprising that many of us are looking for ways to save a little money on our fuel costs.  You may have noticed new options popping up at the fuel station lately, in the form of different grades of gasoline fuel for your car. While "standard" and "premium" gas have been the typical choice for many years, more and more gas stations are offering some additional options. This includes two varieties of fuel that have higher fractions of  biofuel in their formulation:

• Unleaded88 - this is gasoline with 15% ethanol - it's often also called "E15" for that reason. It is usually less expensive than regular gas, and the pump is usually color-coded blue.
• Flex Fuel - this is fuel that is mostly ethanol. The percentage of ethanol ranges from 51-83%. It is usually the least expensive option on a per-gallon basis, and the pump is usually color-coded yellow.

While not every gas station has these new options available at the pump, an increasing number of gas stations are adding them to their lineup, giving drivers some new choices to make.  And while price is not the only consideration when choosing a fuel, the recent period of high gasoline prices has prompted many of us to wonder if either Unleaded88 or Flex Fuel might be an option for their vehicle.  

Can I Use Higher Percentage Ethanol Blends?

In general, cars in the US that have been manufactured since 2001 are approved to use Unleaded88. Older cars may have issues with Unleaded88 due to either the engine sensors and controls not being able to adjust optimally or due to older materials being used for hoses and gaskets that aren't compatible with the higher concentration of ethanol. Unleaded88 has a slightly higher octane rating than regular gas (that's good), but the total energy content per gallon is about 1.5% less (that's not as good).

Flex fuel, which is the commercial fuel with the highest percentage of ethanol, is only rated for use in vehicles that are "flex fuel" approved. Most flex fuel cars have a "flex fuel" symbol affixed to the back of the car (like the photo shown above), but you can check your owner's manual or contact the manufacturer to make sure. 

Does It Pay Off?

From an economics perspective, if Unleaded88 is more than 1.5% less expensive than regular gas, then you should be saving money by opting for Unleaded88. For example, if regular gas is $3.99 but Unleaded88 is $3.69, the Unleaded88 is only 3.69 / 3.99 = 0.92 or 92% as expensive. That means you'll be paying 8% less for fuel that has 1.5% less energy per gallon. In Pennsylvania, Unleaded88 appears to be about $0.30 cheaper than regular gasoline at present.

However, the best way to confirm the savings is to try it out by measuring your car's mileage on a tank of Unleaded88 and comparing that to a tank of Regular in order to know for sure. The same approach works for flex fuel - the best way to know if it is a good deal for your vehicle is to measure the mileage from a tank of flex fuel, and compare that to the vehicle's mileage when using regular gasoline. Are you able to get more "miles per dollar" from flex fuel, from Unleaded88 or from regular?

When Should I Be Extra Careful?

Some people continue to be very concerned about the effect of fuel ethanol on engines. While wild and impressive stories of ethanol catastrophe abound in some circles, scientific studies have not unearthed dramatic cause for concern^1,2,3. So, if your car was made in 2001 or later, feel free to give Unleaded88 a try.  If you car is rated for flex fuel, you should be free to select whichever fuel you prefer. However, there are a few special situations that deserve attention.

• If you are a car hobbyist who has made special aftermarket modifications or added unusual extra parts, you should be careful to make sure your changes are compatible with the fuel you use.
• For those of us with classic cars, extra caution is needed. Not only are older gaskets and seals prone to leak when exposed to ethanol, it's also not unusual for old engines (especially those with carburetors) running hotter when using ethanol blends, necessitating adjustments to the fuel-air mix to keep it operating in the optimal range.  Opting for regular or "ethanol free" fuel may be worth considering in those situations.
• Also, if your car sits for long periods of time between use, it's important to use fuel stabilizer additives to reduce the likelihood of problems - regardless of the grade of fuel you use. However, this is especially important for ethanol blends and for small engines that may not be as precisely designed or maintained.  When ethanol blended fuel was first introduced in the United States, many people noticed increased problems with clogging of fuel systems on their winter-stored lawnmowers and similar small engines that were not used regularly. This is likely due to the tendency of ethanol blend fuels to absorb moisture from the atmosphere during long term storage⁴.

Is It Good For the Planet?

Are fuels with higher ethanol concentrations better for the ecosystem? This is a complex question, as it involves all of the steps from growing the biofuel crops through manufacturing the fuel and transporting it to the gas station, as well as its final use in your car. Many assumptions have to go into that analysis, and those assumptions can have big impacts on the results of the analysis. It will probably be several years before enough studies are carried out to allow us to make a reasonably balanced conclusion about this issue. In general, higher ethanol blends do appear to reduce harmful emissions from the exhaust of cars, and ethanol produced and used in the US is less greenhouse gas-intensive than petroleum fuel. Ethanol is renewable, whereas petroleum gasoline is not.

Closing Points

While ethanol blends may seem like a new thing for many of us, it is interesting to note that the Ford Model T was designed to run on gasoline or ethanol. Perhaps that was the original "flex fuel" vehicle?  For many people, the pros are outweighing the cons with respect to Unleaded88 and Flex Fuel. Ultimately, however, it's up to you to decide which type of fuel you'd rather use in your vehicle. As a summary, here are the key take-home points for this article:

• Unleaded88 (also called E15) fuel is approved for use in all US cars 2001 and newer.
• "Flex Fuel" is approved only for vehicles that are specifically rated to use high ethanol fuels.  
• The lower price of Unleaded88 often makes it a more cost-effective option than regular gasoline.
• You get to choose which fuel you want to use.

If you'd like to learn more, you can read our extension article "Ethanol Fuel: Hero or Villain?".

References: 

1. McCormick, R. L., Yanowitz, J., Ratcliff, M., & Zigler, B. T. (2013). Review and evaluation of studies on the use of E15 in light-duty vehicles. Prepared for the Renewable Fuels Association2013, National Renewable Energy Laboratory: Golden, CO, 53.

1. R. Bechtold, J. F. Thomas, S. P. Huff, J. P. Szybist, T. J. Theiss, B. H. West, M. Goodman, T. A. Timbario, Technical Issues Associated with the Use of Intermediate Ethanol Blends (>E10) in the U.S. Legacy Fleet:  Assessment of Prior Studies, ORNL/TM-2007/37, Oak Ridge National Laboratory, August 2007.

2. Keith Knoll, Brian West, Wendy Clark, Ronald Graves, John Orban, Steve Przesmitzki, Timothy Theiss, Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines, Report 1—Updated, ORNL/TM-2008/117, February 2009.

3. Brent A. Shoffner, Ryan D. Johnson, Martin J. Heimrich, and Michael D. Lochte, Powertrain Component Inspection from Mid-Level Blends Vehicle Aging Study, ORNL/TM-2011/65, Prepared by Southwest Research Institute for Oak Ridge National Laboratory, November 2010.

4. Jęczmionek, Ł., Danek, B., Pałuchowska, M., & Krasodomski, W. (2017). Changes in the quality of E15–E25 gasoline during short-term storage up to four months. Energy & Fuels, 31(1), 504-513.