Explainer: Methanol is good in petrol, bad for engine when excess

The ‘dirty petrol’ currently in Nigeria, which the government has been trying to take out of circulation, has been noted to contain methanol. The Nigerian Midstream and Downstream Petroleum Regulatory Authority (NMDPRA) had said a methanol quantity above Nigeria’s specification was discovered in the petrol supply chain. This specification and what was found, was not disclosed.

However, having methanol in the fuel supply is not unexpected; it only has to be within certain limits, which for Nigeria has not been made public even though different countries also have their methanol limits.

“Methanol is a regular additive in petrol and is usually blended in an acceptable quantity. To ensure vehicular and equipment safety, the limited quantity of the impacted product has been isolated and withdrawn from the market, including the loaded trucks in transit,” NMDPRA said.

Adding alcohols such as ethanol and methanol to petrol allows the fuel to combust more completely due to the presence of oxygen, which increases the combustion efficiency and reduces air pollution, as noted by a Science Direct article. However, when in excess, as noted by another publication the corrosive effects of methanol become a concern.

More than half of the cylinder blocks for car engines are made from aluminum, which incidentally is very prone to corrosion by methanol, which would also affect other components such as gaskets and rubber hoses. This, however, becomes a problem only as the methanol content in a fuel becomes higher than permitted.

When the engines and components get corroded due to substances such as methanol, the outcomes include damage to the engine, which if not detected and rectified where possible, could render it useless.

Read also: Dirty petrol: Government to compensate owners of damaged cars

The current incidence of methanol in Nigeria’s petrol can be likened to something good being abused, and in the end, giving a bad outcome. It can also be seen as a cheap additive being added in excess to cut costs on petrol that would still be sold at the standard price, hence additional profit-making as an objective.

According to the Methanol Institute, methanol is a clean-burning, high octane blending component for gasoline that is made from alternative non-petroleum energy sources such as natural gas, coal, and biomass. Methanol with co-solvents has been commercially blended into gasoline (petrol) at various times and locations since the late 1970s.

In many regions of the globe, the blending of oxygenates such as alcohols and ethers are controlled by government regulations that specify the limits for the various oxygenates allowed in commercial gasoline. As for methanol blending, the maximum limit in gasoline had generally been established based on the compatibility of the non-metal materials of the older vehicles on the road at the time that the regulation was being established.

Although fuel system material compatibility (metals and non-metals) concerns during the commercial introduction of methanol blending during the early 1980s had initially limited methanol content to 5 percent or less in Europe and US markets. The advancement of fuel systems materials and the improvement of corrosion inhibitors to address the growing use of alcohol blends such as ethanol (up to 25% in Brazil) in global markets allows today’s vehicles on the road to use much higher levels of methanol with little risk of incompatibility or performance degradation, according to the Methanol Institute’s publication.