The Impact of E85 Use on Lubricant Performance

Ethanol is widely used as a gasoline component to provide a prescribed amount of oxygenates and for its perceived advantages of less dependence on petroleum based products and lowering overall CO₂ emissions. In most cases the level of ethanol in gasoline does not exceed 10%. In some parts of the Unites States, E85 fuel consisting of 85% ethanol and 15% gasoline is commonly available. Many US vehicles sold today are specially adapted for use of both gasoline and high ethanol fuels; so-called Flexible Fuel Vehicles (FFV). While high ethanol fuels are currently a small percentage of the overall gasoline pool, they provide an interesting opportunity to study the effects that ethanol use in gasoline may have on lubricant related performance.

Based on past industry experience with methanol based fuel, theoretical areas of concern for ethanol based fuels are valve train rust and potential problems associated with high amounts of water in the lubricant. The authors have studied the lubricant related effects of E85 use in well controlled field testing under cold climate conditions. It is concluded that the use of E85 fuel leads to significantly higher water levels in the lubricant as compared to the use of gasoline. The use of E85 does not promote the formation of valve train rust in FFV engines run on modern lubricants.