Ethanol may be added to gasoline to achieve a number of goals.

Designation: E (for ethanol) + (percent ethanol)

Example: E10 is 10% ethanol, 90% gasoline.

Example: E100 is 100% ethanol, 0% gasoline


Common ethanol-fuel mixtures: E5, E10, E15, E20, E25


Ethanol flex fuel has between 51 and 83% ethanol and is suitable for a flex fuel vehicle. E85 was the former designation of flex fuel.


Negative effects:

(1) lower energy potential vs unaltered gasoline (95-98% for each 10%)

(2) damage to seals, pistons and other engine components

(3) more rapid degradation

(4) water absorption


Positive effects:

(1) cleaner emissions

(2) less dependency on foreign oil sources

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