Ethanol is a common additive to gasoline that helps it burn more completely and reduces harmful emissions. Gas stations across the United States stock fuel blended with 10 percent ethanol, and most cars on the road today can handle this fuel mix without difficulty. Ethanol can cause increased wear on your engine, however, and using a higher blend than recommended can lead to serious problems.
Alcohol and Water
One major problem with ethanol and engines is that alcohol absorbs water, and enough water inside your gas tank can cause your car to stall. This problem occurs most frequently when you have very little fuel in your tank and it sits for a long time, allowing the alcohol-and-water mix to settle to the bottom, where the engine will draw it in instead of gasoline. To avoid this, replace the fuel in your tank frequently. You can also opt for a higher octane, 89 or above, to reduce the chances of your engine failing to turn over.
Seals and Gaskets
In some cases, ethanol can corrode rubber and plastic parts inside older-model cars. While modern vehicles have systems designed for ethanol fuel, storing ethanol for long periods can lead to a growth of acidic bacteria in the alcohol mixture that can accelerate damage to these delicate gaskets and seals. If you have to store a vehicle with ethanol fuel in the tank, consider adding a fuel stabilizer specially designed for E10 to prevent bacterial growth and acidification of the fuel.
While almost all vehicles on the road today support E10 gasoline, the ethanol industry has begun producing a 15 percent blend of ethanol, or E15. The higher concentration of ethanol can intensify engine problems, especially in older cars. Only flex-fuel engines or models from 2012 or later should adopt this fuel blend, and you should check your owner's manual before filling up. Using E15 in a vehicle not certified for this fuel can void your warranty and leave you on the hook for costly repairs.
E85 Flex Fuel
Some gas stations offer a new fuel blend containing 85 percent ethanol to 15 percent gasoline, called E85 or flex fuel. This ethanol blend is only for vehicles specifically designed to use it, and in a non–flex fuel vehicle it could cause the engine to stall. If you have added only a few gallons of E85 before realizing your mistake, you can dilute it with regular gasoline, but if you fill up the tank with this fuel you may need to pump it out and replace it. Undiluted E85 fuel in a normal vehicle can greatly increase the chances of seal or gasket damage.