E85 has a corrosive effect on certain engine components that gasoline doesn't, and the different combustion characteristics can lead to:
* Reduced fuel efficiency: You won't get the mileage you expect from either fuel.
* Engine damage: Components may not be compatible with the ethanol, leading to corrosion or premature wear.
* Driveability issues: Rough running, misfires, and other performance problems are common.
* Sensor issues: Ethanol can affect various sensors leading to incorrect readings and potential damage.
If your truck is designed for E85, it will explicitly state this in the owner's manual and often have specific fuel filler markings. Since you're asking this question, it's highly likely your 5.9L Ram is *not* designed for E85. Stick to regular gasoline as specified in your owner's manual.
