Which fuels contain MTBE?

MTBE (methyl tert-butyl ether) appears mainly in gasoline—especially reformulated and some premium blends—as an oxygenate and octane booster. In 2025 it is rare in the United States and Canada, still permitted and used to varying degrees in parts of Europe, widely used in China and some Middle Eastern countries, and present in certain Mexican and Latin American gasoline pools; it is not used in diesel, jet fuel, or aviation gasoline. This article explains where MTBE shows up, where it does not, why policies differ by region, and how to tell whether your fuel contains it.

Where MTBE shows up in the fuel market

MTBE’s primary role is to raise octane and add oxygen to gasoline to help reduce carbon monoxide and certain smog-forming emissions. Its use has shifted over the past two decades: many North American jurisdictions replaced MTBE with ethanol due to groundwater contamination concerns, while several other regions continue to rely on MTBE within their gasoline specifications.

Gasoline types that may contain MTBE

The following categories of gasoline are most likely to contain MTBE, depending on regional regulations and refinery practice:

• Reformulated gasoline (RFG): In markets that still use ether oxygenates, RFG may include MTBE to meet emissions performance; historically common in the U.S. before the mid‑2000s phaseout, and still used in some countries’ urban air-quality programs.
• Conventional unleaded gasoline in MTBE-allowing countries: Standard retail gasoline in parts of Europe, China, the Middle East, Mexico, and some Latin American and Asian markets can include MTBE for octane and oxygen content.
• Premium/high-octane gasoline: Higher-octane grades in MTBE-permitting regions may use MTBE to meet octane targets while controlling aromatics and vapor pressure.
• Seasonal/oxygenated gasolines: Where winter oxygenation programs exist and ethanol is not preferred or available, MTBE may be used as the oxygenate.
• Specialty racing gasolines and certain octane boosters: Some oxygenated racing fuels and performance additives include MTBE or related ethers; always check the product’s safety data sheet (SDS).

In short, if you are in a country that allows ether oxygenates in gasoline and ethanol is not mandated or widely used, there is a reasonable chance retail or premium gasoline may contain MTBE, typically in the single‑digit to low‑teens percent by volume range.

Fuels that typically do not contain MTBE

Several fuel categories either prohibit MTBE, have no technical need for it, or use alternative components to meet specifications:

• Diesel fuel, biodiesel blends, and heating oil: These products are not oxygenated with MTBE and are formulated very differently from gasoline.
• Jet fuel (kerosene) and aviation gasoline (avgas): MTBE is not used; avgas octane is managed with different chemistries, and jet fuel is a kerosene-based product.
• Ethanol-blended gasoline in North America (e.g., E10, E15, E85): Ethanol provides the oxygen and octane, and in the U.S. and Canada MTBE has been largely removed from retail supply due to state/provincial restrictions and liability concerns.
• Prepackaged alkylate small‑engine fuels: These premium, ethanol‑free fuels are generally formulated without MTBE.

If your fuel falls into these categories—especially ethanol‑blended gasoline in the U.S. and Canada or any non‑gasoline distillate fuel—it is very unlikely to contain MTBE.

Regional status in 2025

MTBE usage varies significantly by jurisdiction, driven by air-quality mandates, fuel-quality standards, and water protection policies. Here is a current snapshot:

• United States: MTBE is largely phased out from on-road gasoline. Many states restrict or ban it, and federal reformulated gasoline no longer carries an oxygen mandate. Ethanol now dominates as the oxygenate; MTBE may persist in some specialty racing fuels but is uncommon at retail pumps.
• Canada: Generally not used in retail gasoline; several provinces moved away from MTBE in the 2000s. Ethanol blends are prevalent.
• European Union and United Kingdom: MTBE is permitted by the EN 228 gasoline standard (commonly up to 15% v/v, subject to overall oxygen limits). Use varies by country and refiner; ETBE and ethanol are also common oxygenates.
• China: MTBE remains widely used as a gasoline blend component for octane and oxygen content across many provinces.
• Middle East (e.g., Saudi Arabia, UAE, Kuwait): Regional producers manufacture MTBE and commonly blend it into motor gasoline.
• Mexico: Both MTBE and ethanol are used, with regional practices shifting based on supply, policy, and air-quality considerations; check local specifications.
• Latin America (outside Mexico): Mixed picture—Brazil relies chiefly on ethanol; other countries may use MTBE where ethanol logistics are less developed.
• Asia-Pacific beyond China: Some markets (e.g., parts of East Asia) continue MTBE use; others rely more on ethanol or different octane strategies. Australia generally avoids MTBE, with restrictions in some states.

The net result is a patchwork: in North America MTBE is largely absent from retail gasoline, while in parts of Europe, Asia, the Middle East, and some Latin American markets it remains an accepted blending component.

How to tell if your fuel contains MTBE

Because pump labels typically focus on ethanol content, confirming MTBE requires checking documentation or asking suppliers. These steps help:

• Review local regulations and pump labeling: U.S. and Canadian pumps usually disclose ethanol but not MTBE; in other regions, label practices vary.
• Check the product specification or safety data sheet (SDS): Refiners and distributors can provide documents that list MTBE if present.
• Ask your supplier or marina: This is especially important for bulk deliveries and racing fuels.
• Use laboratory analysis if required: Gas chromatography/mass spectrometry (GC‑MS) can confirm MTBE content for compliance or environmental assessments.

When in doubt—particularly for specialty or imported fuels—documentation from the supplier is the most reliable way to determine MTBE content.

Technical background and limits

MTBE increases octane and can contribute oxygen (improving combustion under certain conditions). It blends readily with gasoline but is highly water‑soluble compared to hydrocarbons, which is why leaks can contaminate groundwater. Regulations cap how much can be added:

• Typical blend levels: Where used, MTBE is commonly blended at about 5–15% by volume, balancing octane, vapor pressure, and oxygen limits.
• European standard (EN 228): Allows MTBE up to roughly 15% v/v, subject to overall oxygen content limits (commonly 2.7% m/m for standard petrol and higher oxygen limits for E10 grades).
• United States policy context: The federal oxygen requirement for reformulated gasoline was removed in 2005; many states restrict or ban MTBE due to groundwater concerns. Ethanol and refinery process changes now provide needed octane and emissions performance.

These limits and practices reflect a balance between engine/emissions performance and environmental protection, with different regions preferring different oxygenates to meet their goals.

Environmental and health context

MTBE’s phaseout in many places stemmed from its tendency to migrate with groundwater and impart taste/odor at very low concentrations if leaks occur. While toxicological assessments vary by jurisdiction, the decisive factor in policy shifts was typically water resource protection rather than tailpipe performance.

• High mobility in water makes spills and leaking tanks a greater concern versus many hydrocarbons.
• Detectable taste and odor occur at low parts‑per‑billion levels, driving public complaints and remediation costs.
• Alternatives such as ethanol or different octane strategies (isomerates, alkylates, aromatics) have replaced MTBE where risks were deemed unacceptable.

Consequently, many regulators opted for oxygenates and octane sources that pose fewer groundwater issues, even if refining strategies had to adapt.

Summary

MTBE is used primarily in gasoline as an oxygenate and octane booster. In 2025 it remains present in parts of Europe, China, the Middle East, Mexico, and some other markets, and in certain racing fuels, but it has been largely removed from retail gasoline in the U.S. and Canada. It is not used in diesel, jet fuel, or aviation gasoline. To know whether your fuel contains MTBE, consult the supplier’s specification or SDS and check local regulations.

What products contain MTBE?

In the U.S. MTBE has been used in gasoline at low levels since 1979, replacing tetraethyllead (TEL) as an antiknock (octane rating) additive to prevent engine knocking. Oxygenates also help gasoline burn more completely, reducing tailpipe emissions.

Is MTBE in diesel fuel?

1996;Pankow et al. 1997). MTBE is added intentionally to gasoline, but may also be found incidentally in other petroleum products, such as heating oil and diesel fuel, probably as a result of contamination during transport ( Robbins et al. 2000 ).

What is MTBE in oil and gas?

MTBE(methyl tertiary-butyl ether) is a chemical compound that is manufactured by the chemical reaction of methanol and isobutylene. 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.

Is MTBE still added to gasoline?

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.