In Focus
July 2022

The harm of gasoline blended with Methylal

The harm of gasoline blended with Methylal

In October 2020 a study about “The harm of gasoline blended with Methylal” was published by China’s Chemicalbook Inc., which is regarded as on the country’s most-visited and largest professional platforms on chemical services. The findings of the report were exposed in CCTV's 3.15 party TV show. In response to the "Methylal Blended Gasoline" documentary exposed by the 3.15 party, "China Consumer News Auto Weekly" conducted and published their investigations about "Methylal Blended Gasoline" through a series of investigations and interviews.

Below the reader will find some of the key finding and observations of the TV show and “Consumer News Auto Weekly” and the full Chemicalbook study can be found under

What is the Methylal?

Methylal (Dimethoxy-Methane) is a colourless, clear, volatile and flammable liquid, mainly used in pesticide formulations, leather and car glazing. The product has a density of 0.86 and an octane reading of <90.

In the 15-March 2021 CCTV show in China it was reported that Methylal has found its way into gasoline blending as a cheap source of octane, passing national quality tests. However, experts warn Methylal-contained gasoline can “easily cause oil leakage in automobile lines" and it can also "volatilize harmful gases", referring to it as "poisonous gasoline".

"Bonding itself is actually an essential processing link in the production of gasoline and diesel. The main raw materials for blended gasoline include catalytic gasoline, mixed aromatics, MTBE (methyl tertiary butyl ether), C5, C9, and naphtha (light oil), etc. (Blending of)) such raw materials can reach national standards after a certain proportion of reasonable deployment.” Geng Ning, R&D department commissioner of China National Chemical Corporation Bluestar (Beijing) Chemical Co., Ltd., told China Consumer News Auto Weekly.

The "smart" use of Methylal

The main reason for the emergence of the pesticide ingredient, together with other harmful chemicals, is its low cost. Blending of refined gasoline with so-called “blended gasoline” is a common process used by oil companies and “blended gasoline”, containing undesired substances, has long existed in the fuel market. An insider of China National Petroleum Corporation (PetroChina) told China Consumer News Auto Weekly that such raw materials have certain blending defects and are not suitable for gasoline. However, “blended gasoline” has been implicitly and yet illegally used by the industry.

What damage is caused by the long-term use of blended gasoline?

China Consumer News Auto Weekly stated in its report that the use of blended gasoline, containing harmful chemicals, will not only cause damage to the vehicle engines and human health, but also cause environmental pollution and bring about the formation of hazy weather. The damage to automobile engines, three-way catalytic converters and other equipment is caused by the unstable condition of hazardous chemicals in blended gasoline. The report points out that blended gasoline, containing Methylal and other harmful substances, may look cheap on the surface, but it may not save money. It may increase a vehicle’s fuel consumption by blocking the fuel nozzle and forming deposits. Long-term use of these qualities of blended gasoline streams directly affect the normal operation of gasoline engines and the car’s performance.

Wang Xin, Engineering Technology Department of China National Chemical Corporation Bluestar (Beijing) Chemical Co., Ltd. stated that long-term addition of blended gasoline will damage the 3-way catalytic converter of the car and corrode the car engine system and emission system. The engine fuel circuit will be damaged during the combustion process. The fuel nozzle may get blocked by the formation of gums and carbon deposits in the intake valve and cylinder, which directly affect the normal operation of the gasoline engine.

The long-term danger and serious consequences of human exposure to Methylal was also highlighted. Blended gasoline containing Methylal and other hazardous ingredients could cause chronic poisoning of the human body and also cause gradual changes in the respiratory system and central nervous system. In severe cases it may even develop into cancer.

"The quality of blended gasoline is completely controllable. In 2011, PetroChina had clearly stipulated that Methylal should not be contained in externally-produced gasoline”, a representative of the China National Petroleum Corporation (CNPC) told China Consumer News Auto Weekly on the issue of oil monitoring and management compatibility. However, the current market is predominantly focused on price advantages among competitors, which have triggered quality adjustments. Retailers show no conscience, and the market does not have a clear industry standard and lacks a regulatory mechanism. While similar in appearance, blended gasoline containing Methylal is cheaper than refined gasoline. “It is difficult for ordinary consumers to accurately identify which is better and which is worse”, the CNPC representative added.

To recapitulate, the use of harmful chemicals goes against China's intentions and major efforts in recent years to improve the country's air quality, which ACFA strongly supports. Vehicle emissions and the protection of human health have emerged as top priorities in the policy and regulatory process. China has included exclusion clauses for harmful chemicals in its GB V and GB VI fuel specifications, which consumers should also appreciate as it extends the engine life of their vehicles.

China has banned most chemical additives in its gasoline standard directive GB17930-2013 (GB-V) and GB 17930-2016 (GB-VI), which states that “Additives used in gasoline for motor vehicles should not contain recognised harmful substances and should be used by following up with the recommended safe dosage. Chemicals, such as Methylal, aniline-type compounds, halogens and those containing phosphorus and silicon, etc. should not intentionally be added in gasoline.”  

State-owned refiners have implemented additional test parameters for gasoline, which has been purchased from third parties. NMA, total anilines, sec-methyl acetate and Methylal, etc. should not be detected or should remain below detectable limits, using a middle infrared analyser.

However, the case discussed here appears to require further attention. Specifications in the retail market as well as at petrol stations for certain additives currently in use need to be redefined and restricted, and testing methods and quality controls need to be adjusted.

The use of harmful substances in fuels has also been addressed in other countries in Asia. Singapore for example does not allow any addition of metallic additives and is restricting the use of chemical additivities. The industry refers to a 100 ppm Acetone limit. Singapore has adopted the environmentally cleaner Euro 6 fuel emission standards for domestic vehicles powered by petrol in September 2017. Beyond this, the National Environment Agency (NEA) implemented new parameters for gasoline under Singapore’s Environmental Protection and Management (Vehicular Emission) regulations as from 01-July 2019. The NEA stated its purpose as to further reduce air pollution and safeguard public health. Among others, restrictions for methyl cyclopentadienyl manganese tricarbonyl, commonly known as MMT, and phosphorus were introduced, with MMT limited to max 2.0 mg/l, while the addition of phosphorus has been prohibited.

ACFA welcomes any readers’ comments and requests to discuss this topic further. Detailed insights and data on the use of harmful additives in gasoline can be provided.  

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