Pure ethanol becomes difficult to vaporize when cold, leading to poor cold startability. In fact ethanol will not form an air/fuel vapor mixture high enough to support combustion below 11 °C.12 Therefore, gasoline is added to the ethanol in order to support cold startability and increased cold start enrichment is used to achieve combustible vapor air mixtures in the engine.

Additional difficulties when cold starting with E85 can be attributed to its high conductivity. During cold starts, the spark plug electrodes can become wetted with fuel. Since E85 is much more conductive, this can leading to plug shorting and misfire.8

These problems have been addressed by the major automakers through better cold-start fuel calibrations. Most manufacturers now report good cold starts at temperatures below 0°F (-18°C) when using E85 in a winter blend (E70).

Safety

E85 has wider flammability limits on the rich side, and it has a higher flame speed compared to gasoline. This increases the probability of encountering flash­back or fuel vapor ignition during fuel filling.17 Because of this, vehicles using

E85 require a flame arrestor, which is installed into the fuel filling tube. This device will extinguish any flame that might occur.