Is MTBE used in gasoline?

Yes—but mostly outside the United States. As of 2025, methyl tert-butyl ether (MTBE) remains in use as a gasoline blending component in several regions worldwide, particularly in parts of Europe, Asia, the Middle East, and Latin America. In the United States, MTBE is not federally banned but has been largely phased out of retail gasoline since the mid-2000s due to state-level restrictions and contamination concerns; ethanol has become the dominant oxygenate instead.

What MTBE is and why it was used

MTBE is an oxygenate and high-octane blending component that refiners began adding to gasoline in large volumes in the 1990s to help reduce tailpipe carbon monoxide and ozone-forming emissions. In the U.S., its use expanded under the Clean Air Act’s reformulated gasoline requirements, which encouraged oxygenated blends to meet air-quality goals. MTBE’s favorable blending properties—high octane, low vapor pressure—made it attractive to refiners.

Current status by region

United States

MTBE use in mainstream U.S. retail gasoline effectively ended in the mid-2000s. Multiple states—including California and New York—banned MTBE after widespread detections in groundwater tied to leaking storage tanks, and refiners shifted to ethanol. The Energy Policy Act of 2005 removed the federal oxygenate mandate for reformulated gasoline (effective 2006), while the Renewable Fuel Standard drove broad ethanol adoption (E10 nationwide, with growing E15 availability). MTBE is not federally prohibited, but it is rarely, if ever, present in regular road gasoline today; niche applications such as certain racing fuels may still use ethers.

Canada

Canada does not have a nationwide prohibition, but several provinces imposed restrictions or bans in the 2000s, leading refiners to move away from MTBE. As in the U.S., ethanol-blended gasoline is the norm, and MTBE is seldom used in retail fuels.

European Union and United Kingdom

MTBE remains permitted under European standards. The petrol specification EN 228 allows MTBE up to defined limits (commonly cited as up to 15% by volume), alongside other ethers such as ETBE and TAME, subject to overall oxygen content caps. Many EU blends use ETBE (made from ethanol) to help meet renewable-content objectives, but MTBE is still used in some markets depending on refinery configurations and policy choices. The UK maintains similar specifications post-Brexit.

Asia, Middle East, and Latin America

MTBE continues to be produced and used widely in several countries, supported by regional petrochemical capacity and gasoline quality targets. China, parts of the Middle East (which host major MTBE plants), and some Latin American markets incorporate MTBE as an octane booster and oxygenate. Elsewhere in the Americas—particularly Brazil and parts of the U.S.—ethanol dominates.

Why MTBE declined in North America

MTBE’s high solubility in water and strong taste/odor at very low concentrations made groundwater contamination incidents costly and conspicuous. As detections mounted in the late 1990s and early 2000s, states enacted bans or restrictions, litigation risks grew, and refiners opted to switch to ethanol. Federal policy shifts reinforced this transition: the 2005 Energy Policy Act eliminated the reformulated gasoline oxygenate requirement, and the Renewable Fuel Standard (expanded in 2007) created strong incentives for ethanol blending. Recent U.S. moves to expand year-round E15 availability in several Midwestern states from 2025 further underscore ethanol’s central role.

How to tell if your gasoline contains MTBE

Consumers rarely see MTBE listed at the pump, and labeling often focuses on ethanol content. If it is important to verify whether MTBE is present, the steps below can help clarify what’s in a specific fuel.

• Look for pump decals: In the U.S., pumps typically state “contains up to 10% (or 15%) ethanol.” Such labeling implies ethanol is the oxygenate, not MTBE.
• Check the product Safety Data Sheet (SDS) for the specific grade; refiners and distributors list typical components and ranges.
• Contact the retailer or brand’s technical support for confirmation about oxygenates used in your region.
• Review local fuel specifications (e.g., U.S. state regulations, EU EN 228) that set allowed oxygenates and limits.
• For critical applications, commission a laboratory analysis (e.g., GC-MS) to detect and quantify MTBE and other ethers.

In most U.S. retail contexts, these checks will confirm ethanol—not MTBE—is used. In some international markets, SDS sheets or supplier statements may show MTBE or other ethers in the blend.

Key regulatory milestones

The following timeline highlights policies that shaped MTBE’s rise and retreat, especially in the United States, and the standards that continue to govern its use abroad.

1. 1990: U.S. Clean Air Act Amendments create the Reformulated Gasoline (RFG) program, spurring widespread MTBE adoption as an oxygenate.
2. Late 1990s–2006: Numerous U.S. states enact bans or restrictions after groundwater contamination concerns; California and New York bans take effect in 2004.
3. 2005–2006: U.S. Energy Policy Act removes the federal oxygenate mandate for RFG; refiners rapidly transition away from MTBE.
4. 2007 onward: Renewable Fuel Standard ramps up ethanol blending; E10 becomes standard U.S. retail gasoline, with E15 expanding.
5. EU/UK (ongoing): Fuel Quality Directive and EN 228 specifications permit MTBE within limits (commonly up to 15% v/v) and define total oxygen content caps; ETBE and other ethers also allowed.
6. 2025: EPA approval for year-round E15 in several U.S. Midwest states takes effect, reinforcing ethanol’s role in gasoline blends.

Together, these measures explain why MTBE remains present in several world markets yet is largely absent from U.S. retail gasoline.

Environmental and health considerations

MTBE is detectable in water at very low concentrations due to its strong taste and odor, and it migrates readily with groundwater. Cleanup of contaminated aquifers and wells can be difficult and costly. Toxicologically, international assessments have generally found limited evidence for carcinogenicity in humans; the International Agency for Research on Cancer (IARC) classifies MTBE as Group 3 (“not classifiable as to its carcinogenicity to humans”). California lists MTBE under Proposition 65 as a chemical known to cause cancer, reflecting state-level risk policy. Regardless of classification, the key policy driver was environmental impact—particularly drinking water concerns—rather than tailpipe emission performance, where MTBE had been effective.

Summary

MTBE is still used in gasoline in various regions worldwide, but not typically in U.S. retail fuel. In the United States and much of Canada, MTBE was phased out in the mid-2000s and replaced mainly by ethanol due to groundwater contamination concerns and evolving federal and state policies. In the EU, UK, and several countries in Asia and the Middle East, MTBE remains permitted and is used within specification limits, often alongside other ethers like ETBE. Consumers seeking certainty should consult fuel labels, supplier SDS documents, or local specifications; in most U.S. cases, the oxygenate you’re getting is ethanol.

What is the chemical MTBE used for?

MTBE is primarily used as a fuel additive in gasoline to improve combustion and reduce air pollution, though its use has been largely eliminated in the US due to widespread water contamination and replaced by ethanol and other alternatives. It also serves as a chemical solvent in the production of other compounds, such as resins, coatings, and pharmaceuticals, and has a limited medical use to dissolve gallstones.
 
Main Uses

• Gasoline additive: MTBE was added to gasoline to increase octane and, more importantly, to reduce harmful air pollutants like carbon monoxide by ensuring more complete fuel combustion. 
• Solvent: It acts as a versatile solvent in various chemical and industrial processes to dissolve oils, waxes, and resins. 
• Medical Treatment: MTBE has been used in a medical capacity to dissolve cholesterol gallstones in patients, though exposure to the chemical has potential health risks. 

Other Uses 

• Chemical Intermediate: MTBE can be a reactant or intermediate in the synthesis of other chemicals, including Tertiary Butyl Alcohol (TBA) and isobutene.

Decline in Use

• Water Contamination: MTBE’s use in gasoline has significantly decreased in the United States because it readily dissolves in water and can persist in groundwater, contaminating drinking water supplies even from small leaks. 
• Replacement by Alternatives: Due to the environmental concerns, the use of MTBE as a fuel oxygenate has been replaced by ethanol and other alternatives in the US. 

How much MTBE is added to gasoline?

2 to 15%
Methyl-tertiary-Butyl Ether (MTBE) is added to gasoline at 2 to 15% to improve its combustion performance, especially to lower ozone and carbon monoxide levels in urban areas.

What fuels contain MTBE?

motor gasoline
MTBE is produced in very large quantities (over 200,000 barrels per day in the U.S. in 1999) and is almost exclusively used as a fuel additive in motor gasoline. It is one of a group of chemicals commonly known as “oxygenates” because they raise the oxygen content of gasoline.

Is MTBE still used in gasoline?

MTBE was once commonly used in the United States but was phased out in the late 2000s as a result of water contamination concerns. Since then, fuel ethanol has replaced MTBE as a gasoline additive. MTBE is a fuel oxygenate that boosts octane ratings and helps achieve more complete combustion in gasoline engines.