In recent years an increased number of cases have been observed in which chemical compounds are being blended into gasoline that could have a detrimental effect on engine performance, human health and the environment. The majority of those cases are related to gasoline blends being delivered to Africa, Middle East and Asia, as Europe and the United States have regulations in place that partially prohibit the use of these chemicals.
Considered to be a cheap source of octane, these chemicals could cause engine problems, such as corrosion of engine parts, and could affect driving performance. They are also harmful to human health and to the environment in the long term when blended and burnt in transportation fuels.
Asian Clean Fuels Association (ACFA) has been recently alerted on this subject by governments and the oil industry. Based on the information given to ACFA, we have put together a summary on the non-traditional gasoline additives and their potential effects when blended with gasoline. ACFA intends to further investigate this matter, the results of which could be the subject of a future article. The conclusions of the report can certainly be applied to other countries in the Asian community and will lead to similar results.
The non-traditional gasoline additives (NTGAs) are:
These are organic compounds used as solvents in a wide range of industrial applications. These solvents have recently been detected in gasoline blends and are believed to be linked to several engine performance problems, such as engine start-up and acceleration problems. The use of the chemicals listed above in their targeted applications does not provide any reason for health, safety and environmental concerns and is regulated and monitored i.e. by REACH (Regulation, Evaluation, Authorisation and Restriction of Chemicals), which is the European Union regulation 1907/2006/EC on chemicals, adopted to improve the protection of human health and the environment from the risks that can be posed by chemicals.
1. Review of current policies on blending NTGAs in gasoline
We have reviewed current policies in a number of countries and regions, namely Vietnam, China, the United States and Europe. We also cross-referenced these findings against the World Wide Fuel Charter (WWFC), a document released by engine and vehicle manufacturers from around the world, including North America, Japan and Europe, which recommends diesel and gasoline standards in order to harmonise worldwide fuel quality.
China has banned most chemical additives in the gasoline standard directive GB17930-2013 dated Dec. 18 2013, 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.”
China’s largest refiner, Sinopec Corp., has released additional test parameters for gasoline 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.
NTGAs were not found in the U.S. Environmental Protection Agency’s (EPA) List of Registered Gasoline Additives.
Fuel additives in the United States are regulated under section 211 of the Clean Air Act (as amended in January 1995). The EPA also regularly reviews the health and net economic benefits of U.S. Clean Air Act policies.
Under section 211 of the U.S. Clean Air Act, all refiners and importers must register their fuel additive products with the EPA before these products are sold in the United States. All gasoline and diesel fuel additives produced and commercially distributed for use in highway motor vehicles must be registered with the EPA.
NTGAs are not in the list of recommended oxygenates in European Union (EU) petrol standards.
Referring to EU EN 228:2012 and Directive 2009/30/EC, Automotive Fuels of Unleaded Petrol—Requirements and Test Methods, none of the NTGAs were found in the list of recommended oxygenates, and their use is restricted by the European emission standards, Euro 5/6 standards (2209/2014): Regulation 715/2007.
It was reported that Vietnam had banned the use of SBA as an additive for gasoline after finding high levels of the substance in cargoes imported from Singapore. Its use as an octane booster had never been documented. The impact of SBA, if used as a gasoline additive, on human health and motor vehicles, is not known.
Vietnam has banned acetone as a gasoline additive due to “unknown” human health effects and potential damage to vehicle engines.
NTGAs are not in the list of recommended oxygenates under category 4 of the WWFC, which refers to emission standards for unleaded gasoline for “markets with advanced requirements for emission control.”
In the fifth edition of the WWFC, the oxygen limit was set at 2.7% by mass percentage. It mentions in a footnote that “where oxygenates are used, ethers are preferred.”
2. Hazard and Exposure Levels of NTGAs
The following table summarizes the hazards and exposure levels of the NTGAs reviewed:
All types of NTGAs are categorized as flammable liquids under the United Nations (UN) hazard classification system or, in the case of NMA, as a toxic substance. Some research reports point out that NMA can cause damage to the central nerve system and can also cause liver and kidney failure.
3. Effects of NTGAs on engine and fuel quality
The effects of each of these solvents when blended with gasoline on engine performance and fuel quality are discussed below.
Sec-Butyl Acetate’s strong reaction with acids and oxidants and its strong dissolving ability, which causes a swelling effect on any rubber-based engine parts, may cause engine malfunction when it is used for a period of six hours or more.
Because of its very low vapour pressure, SBA may cause the gasoline blend to fall below the minimum requirement of 40 kPA (in countries that have a minimum vapour pressure specification). Low Reid Vapour Pressure (RVP) levels may lead to evaporation losses and a decrease in fuel efficiency.
A study conducted in China by Liu Jingdong in 2012 showed that adding aniline-type additives can significantly improve the octane number of gasoline. However, its use can at the same time result in gum formation, drastically shorten the induction period, as well as sharply increase seal swell. High gum levels cause higher carbon deposits in engine parts such as pistons. Shorter induction times can cause gasoline stability to decline and antiknock. The swelling of seal rings may cause oils to leak from engine pipes.
The table below highlights the effects of aniline blending on gasoline quality and seal rings:
Add 3% Aniline
Add 5% Aniline
Research Octane Number (RON)
Motor Octane Number (MON)
Induction period (min)
Seal ring swelling*
After 48 hours
Seal ring swelling*
After 96 hours
*(butadiene – acrylonitrile rubber)
The addition of NMA to gasoline could also cause heavier copper strip corrosion, which can lead to engine corrosion. NMA also contains nitrogen. When it reacts with oxygen, the result is nitrogen oxides (NoX), a harmful gas. Gasoline blends with greater than 5% concentration of NMA can cause sediments in the engine combustion chamber, which can cause failure in octane-number reading by anti-knock sensors in the engine’s computer, according to one study.
Acetone is highly reactive to oxidants and has a negative impact on plastics. When blended with gasoline, it can increase seal swell and dissolving risk, potentially causing engine damage.
This solvent has been mainly used as a cheap alternative to other gasoline components, but with a density of 0.86g/m3 and an octane rating of 83-84 RON, it may not be efficient to use this as an octane enhancer. The negative effect of methylal is that it also has swelling effects on plastics and thus could cause damage to any auto parts made of plastic that it comes into contact with.
Methyl Acetate is only sporadically considered for gasoline blending, especially when its solvent value in other chemical applications falls below its blend value in gasoline. Its octane contribution is offset by the product’s high density and vapour pressure of 165 mm Hg at 20 °C.
Methyl acetate can react explosively in the presence of water and plastics, making it highly unsuitable for gasoline blending, as there will be a certain amount of water that ends up in gasoline due to condensation and there are a lot more plastic parts in today’s automobile.
All these solvents show detrimental effects on engine parts which can potentially cause engine damage or, at the least, oil system failure.
Due to their undetermined effects on human health and long-term effects on air and water quality, these NTGAs are already prohibited, not recommended or deselected in a few countries’ gasoline specifications.
Governments and policymakers need to look further into these concerns, and the Clean Fuels industry needs to assist the auto manufacturing industry in its efforts to regulate the use of chemicals that could be harmful to the engine, to human health and the environment.
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