Some of the more popular ethers are MTBE, ETBE, TAME, and DIPE. There are others, but they come with environmental issues, which prevents them from being used as often. MTBE is produced using methanol. Methanol is produced via methane + isobutylene. Isobutylene is produced from butane. Although MTBE is a nice alternative for increasing octane rating in gasoline, it is also under much scrutiny, particularly in the United States, because of it’s potential effects on the environment. In fact, the US oil industry has stopped using MTBE in gasoline on a national level because of traces being found in groundwater, making it undrinkable in most cases. The other ethers face similar groundwater pollutant issues, which has halted their use as octane enhancing alternatives as well. Outside of the US, MTBE continues to be used for octane enhancement.