E85 is a fuel blend of ethanol and gasoline sold for flex-fuel vehicles. Despite the name, the ethanol content varies: the U.S. Department of Energy describes E85 as containing 51% to 83% ethanol, depending on the season and where it is sold. It has a higher octane rating than regular gasoline but less energy per gallon, so a car burns more of it to cover the same distance.
What is E85 made of?
Ethanol is an alcohol, made in the United States mostly from corn. Blending it with gasoline gives fuels named by their ethanol share: most pump gasoline already contains up to 10% (E10), and E85 sits at the high end. Winter blends usually carry less ethanol because pure ethanol is harder to ignite in cold weather.
Which cars can use E85?
Only vehicles designed for it. Flex-fuel vehicles (FFVs) can run on gasoline, E85 or any mix of the two; they are usually identified by a badge, a yellow fuel cap or ring, or a note in the owner’s manual and on the fuel door. Using E85 in a car that is not designed for it can cause poor running, warning lights and damage to fuel system parts that are not ethanol-compatible.
E85 vs gasoline
| E85 | Gasoline | |
|---|---|---|
| Octane | Higher | Lower (regular, midgrade or premium) |
| Energy per gallon | Lower, so fuel economy drops | Higher |
| Fuel volume needed | Noticeably more for the same power | Baseline |
| Cold starting | Harder in cold weather | Easier |
| Availability | Limited to some stations | Everywhere |
Why performance builds use E85
The higher octane rating and the cooling effect of ethanol make the engine more resistant to knock, which allows more boost or ignition advance on supercharged and turbocharged engines. The cost is fuel volume: an engine on E85 needs substantially more fuel than on gasoline, so the pump, lines and injectors must be sized for it, and the engine must be calibrated for the fuel.
What an E85 fuel system upgrade involves
- More pump capacity: a larger pump, or a second pump that switches on under boost.
- Larger lines and fittings that are compatible with ethanol.
- Larger injectors to deliver the extra volume.
- Calibration of the engine computer for the fuel, often with an ethanol content sensor so it can adapt to the blend in the tank.
Converting a vehicle that was not built as a flex-fuel vehicle can conflict with federal and state emissions rules, so check them before changing fuels.
E85 fuel systems we carry
For supercharged mid-2003 to 2013 C5 and C6 Corvettes, the ECS Stage 1 E85 Fuel System ($1,832.60) adds a second pump brought in by a Hobbs switch that reads vacuum and boost, and upsizes the feed hoses to -10AN for E85 flow while keeping the factory fuel rails and regulator. Injectors are not included. A gasoline version, the ECS Stage I Fuel System, is $1,483.90. See them with the kits they support on our supercharger kits by platform and Corvette parts pages.
More guides: fuel injector sizing for E85 · fuel pump sizing for E85 · what is compression ratio? · ethanol in boat fuel.
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