Conversion of alcohols to ethers, i.e. ethanol into ethyl tert-butyl ether (ETBE) or tert-amyl ethyl ether (TAEE) and methanol into methyl tert-butyl ether (MTBE) or tert-amyl methyl ether (TAME), produces gasoline components with excellent fuel properties. From the end-use point of view, ethers are preferred over alcohols as gasoline components. Octane numbers of ethers are high, and thus they have been used as octane boosters in gasoline. Vapor pressures of ethers are low, and blending with gasoline is predictable. Ethers are aromatic-, olefin-, and sulfur-free compounds. In past, MTBE was widely used as an oxygenate in the reformulated gasoline in past. At first, MTBE was introduced as octane booster. Then, widespread usage of MTBE was based on its capability to reduce exhaust emissions. Emissions reductions depend on oxygenate type, blending ratio, the operating conditions, engine characteristics, and many other parameters. CO and HC emissions typically are reduced, but NO_x emissions may increase. Ethers are compatible with current car and fuel distribution chain. Water solubility of ethers is low and thus ethers do not carry phase separation risk or other water related problems.

The main benefits and drawbacks with fuel ethers are listed below.

Benefits of fuel ethers:
+ High octane number help refineries to obtain required octane level
+ No azeotrope with gasoline → predictable volatility blending properties
+ Low volatility helps refineries to obtain required volatility properties
+ Lower VOC emissions than for ethanol
+ General reduction of VOC, CO, HC, and toxic emissions compared to non-oxygenated gasoline
+ Not aggressive towards normal materials
+ Low solubility with water → no phase separation risk
+ Compatible with current cars and infrastructure

Drawbacks of fuel ethers:
- Higher aldehyde emissions when compared to non-oxygenated gasoline
- Higher NO_x emissions when compared to non-oxygenated gasoline (Note: Not necessarily with FFV cars)