When MTBE Was Eliminated from Gasoline

In the United States, methyl tert-butyl ether (MTBE) was effectively eliminated from most gasoline by mid-2006, particularly after May 2006, when refiners rapidly switched to ethanol; earlier state bans—most notably in California and New York in 2004—accelerated the phaseout. There was no single nationwide ban, but a combination of state actions and a federal policy change drove MTBE’s disappearance from the U.S. fuel supply. Internationally, MTBE has not been universally banned and remains in limited use in some markets.

What MTBE Is—and Why It Was Phased Out

MTBE is an oxygenate and octane booster widely adopted in the 1990s to help gasoline burn cleaner under the federal Reformulated Gasoline (RFG) program. Its downside became clear as even small leaks from storage tanks contaminated groundwater, imparting a strong taste and odor at extremely low concentrations and raising health and environmental concerns. The combination of water contamination incidents, cleanup costs, litigation, and public opposition set the stage for its withdrawal from U.S. gasoline.

Key drivers behind the phaseout

The following points explain the main factors that pushed MTBE out of U.S. gasoline in the 2000s.

• Groundwater contamination: MTBE spreads readily and is detectable at very low levels, making cleanup challenging and costly.
• State action: A wave of state bans and restrictions between 2000 and 2006—led by California and New York—curtailed supply.
• Federal policy shift: The Energy Policy Act of 2005 removed the 2% oxygen content requirement for RFG (effective May 2006), eliminating the main regulatory reason to use MTBE.
• Refiner switch to ethanol: With the oxygen mandate lifted and liability concerns mounting, refiners rapidly transitioned to ethanol as the preferred oxygenate/octane source.

Together, these factors made continued use of MTBE uneconomic and risky in the U.S., accelerating an industry-wide transition away from the additive.

Timeline in the United States

While there was no single federal ban date, a consistent sequence of policy and market moves drove MTBE’s exit. Below are the milestone moments that mark the phaseout.

• 1990s: MTBE use expands under the Clean Air Act Amendments’ RFG oxygenate requirement.
• Late 1990s–early 2000s: Groundwater contamination cases mount; utilities and municipalities pursue cleanup and litigation.
• 1999–2003: California orders a phaseout; the state’s ban on MTBE-containing gasoline takes effect January 1, 2004.
• January 1, 2004: New York’s statewide ban also takes effect, reinforcing a broader regional shift.
• August 2005: Energy Policy Act of 2005 is enacted, ending the federal oxygen content mandate for RFG.
• May 2006: With the oxygen mandate effectively lifted, major U.S. refiners remove MTBE from reformulated gasoline; ethanol becomes the dominant replacement oxygenate.
• By late 2006: MTBE use in U.S. gasoline drops to a negligible share; it is effectively eliminated from most consumer gasoline nationwide.

By the end of 2006, the combination of state bans and the federal policy shift had driven a near-complete exit of MTBE from the U.S. gasoline pool, though there was never an explicit nationwide prohibition.

What “Eliminated” Means for Drivers and Fuel Markets

For consumers, MTBE’s exit was largely seamless: pump labels changed little beyond the growing prevalence of ethanol blends (such as E10). For refiners and fuel distributors, the shift required logistical adjustments—chiefly expanding ethanol blending and modifying distribution practices—while maintaining octane and emissions performance standards. The broader outcome was a permanent move toward ethanol as the primary oxygenate in U.S. gasoline.

Outside the United States

The MTBE story varies globally. The European Union has not imposed a blanket ban; MTBE and related ethers remain permitted within fuel-quality limits, though some countries or localities impose restrictions due to groundwater concerns. Many markets have nonetheless reduced reliance on MTBE in favor of ethanol or ETBE. Elsewhere, regulations differ by country, with some jurisdictions restricting or discouraging MTBE while others allow limited use under strict storage and handling rules.

Summary

MTBE was effectively eliminated from most U.S. gasoline by mid-2006, following state bans—especially in California and New York in 2004—and a crucial federal policy change that removed the oxygenate requirement for reformulated gasoline. While not federally banned, MTBE’s U.S. market share collapsed as refiners switched to ethanol. Internationally, MTBE’s status varies, with continued but more constrained use in some regions.

When was MTBE phased out of gasoline?

In 2000, EPA drafted plans to phase out the use of MTBE nationwide over four years.. Some states enacted MTBE prohibitions without waiting for federal restrictions. California banned MTBE as a gasoline additive in 2002. The State of New York banned the use of MTBE as a “fuel additive”, effective in 2004.

Is MTBE banned in the US?

MTBE was added to gasoline in the mid-to-late 1980s to increase fuel efficiency and decrease pollution, with peak usage during the 1990s. When MTBE started to be detected in groundwater, several states banned its use in gasoline and it has not been added to gasoline in the United States since 2005.

What countries still use MTBE?

The demand for MTBE in countries, such as China, India, South Korea, Mexico, and Saudi Arabia, has been increasing due to increased demand for gasoline from the automotive industry, which has been leading to an increase in the gasoline production in the aforementioned countries, in order to cater to the rising demand.

Is MTBE used in gasoline?

Methyl tertiary butyl ether (methyl tert-butyl ether, methyl t-butyl ether, or MTBE) is a chemical compound once commonly used in the United States as a fuel additive in gasoline. It is an oxygenate, meaning it increases the oxygen content of the gasoline, and is also an octane rating enhancer in gasoline.