E15 Gas

E15 gas — pros and cons

What is E15 gas?

E15 gas is a blend of approximately 85% traditional gasoline and 15% ethanol alcohol. It’s rated at either 88 octane.

Why add ethanol to gasoline

Refiners used to use Methyl tert-butyl ether (MTBE) as an additive to replace tetraethyl lead to increase octane and reduce knock. However MTBE is a major pollutant when it enters the water table after being spilled at gas stations and in marine applications.

By 2007, most states had banned the use of MTBE. So refiners had to come up with another additive that would boost octane but not worsen emissions. Ethanol was the answer and E15 and E85 were developed.

E15 is safe for most cars manufactured since 2001 and beyond. However, it may cause problems with the rubber used in earlier model vehicles.

Pros of E15

E15 is cheaper than 100% gasoline or E10 and the MPG is about the same as E10.

Ethanol for use in gasoline is produced using corn and a fermentation process. The production process has been refined to the point where producing ethanol no longer uses more energy than the amount of energy contained in the alcohol itself.

So it helps the farming industry while increasing the octane and oxygen content in fuel.

E15 burns cleaner than 100% gasoline, but burns about the same as E10 fuel.

Cons of E15

In summer months, the alcohol evaporation from E15 can cause ground-level air pollution that reacts with sunlight to form smog.

The biggest drawback to E10 and E15 fuel is that ethanol is “hygroscopic” and adsorbs water. When E10 and E15 reach their limit of water adsorption there are subject to “phase separation,” where the ethanol/water component separates from the gasoline and falls to the bottom of the tank.

Phase separation is especially problematic in small engines that use carburetors. The ethanol water component tends to corrode and clog the small passageways in carburetors.

What vehicles can use E15?

Vehicles made after 2001 can use 100% gasoline, E10 and E15 with no problems.

E15 should not be used in small engines.

E15 should NOT be confused with E85 which is 85% ethanol and 15% gasoline and is referred to as a “Flex Fuel.”

©, 2022 Rick Muscoplat