Rick's Free Auto Repair Advice

E85 Gasoline

What is E85 gas?

E10 gasoline is 10% ethanol and 90% gas. So it’s no surprise that people think E85 is 15% ethanol and 85% gasoline. It’s not. In fact, it’s just the opposite. E85 Gasoline can be as high as 85% ethanol and 15% gasoline. However, E85 Flex Fuel is allowed to be made within a wide range, from as low as 51% ethanol, up to 85%. Ethanol is 105 octane. That means it is much more resistant to detonation (igniting from the heat of compression instead of the spark plug). But you can’t run E85 in a vehicle that’s not designed for it. You can only run E85 in Flex Fuel cars.

The downside to E-85 is that it contains 27% less energy than E10. So you’ll get approximately 27% fewer miles per gallon. When E-10 prices are high, you may come out ahead using E-85 in your Flex Fuel vehicle. But the math really depends on the current market prices for ethanol.

The other downside is that the U.S. Government subsidizes the production of Ethanol. In the early days, it took more energy to create a gallon of ethanol than it provided in your car. However, manufacturing efficiency has improved and it now takes less energy to make it than it provides. Whether the ethanol industry deserves continued subsidy is a political question I won’t address here.

The upside to E85 is reduces some emissions. But it also raises others. It’s not a perfect fuel.


© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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