TEMPO.CO, Jakarta - Executive Director of the Committee for the Elimination of Leaded Gasoline (KPBB) Ahmad Safrudin explained the various impacts that consumers experience from the use of adulterated gasoline. This explanation relates to complaints from several Surabaya residents about their motorcycles stalling while in use.
"The impact felt by consumers who use motor vehicles, first and foremost, is the occurrence of knocking and engine stalling," he said during a discussion in Jakarta on Thursday, November 27, 2025.
According to Safrudin, knocking occurs when gasoline with an insufficient octane rating is used in vehicles designed to higher technological standards. Indonesia has adopted Euro 2 emission standards since 2007 and upgraded to Euro 4 in 2018. Vehicles produced after 2007 have a minimum compression ratio of 9:1, requiring gasoline with the corresponding octane rating. "So, if it is filled with pertalite, which has an octane rating of 90, it will definitely cause knocking," he explained.
The decrease in the octane rating of mixed gasoline, primarily due to the loss of ethanol's octane-boosting function, forces vehicles to operate at 88–89. As a result, approximately 20 percent of the fuel does not burn completely.
Safrudin added that knocking occurs when the gasoline burns prematurely before the spark plug ignites. The combustion process becomes suboptimal, leading to high emissions. Around 20 percent of the gasoline in the vehicle does not burn.
"Wasting fuel into the exhaust will result in high levels of hydrocarbons, high levels of carbon monoxide, high levels of nitrogen dioxide, and high levels of particulate matter, causing air pollution around us," he said.
In addition to fuel losses, knocking can also trigger mechanical damage. Safrudin stated that abnormal vibrations in the piston can accelerate wear and reduce the precision of the engine block, potentially requiring an engine overhaul.
Ethanol also has a hygroscopic effect on the gasoline mixture, making it easier for water to mix evenly in the tank. This condition increases the risk of water being drawn into the combustion chamber, contaminating the fuel pump, clogging injectors, and damaging spark plugs. "The spark plugs also become dirty, and can even be damaged," said Safrudin.
Damages could spread to expensive components such as the catalytic converter or exhaust gas filter. Due to the potential for various damages, Safrudin emphasized that consumers using adulterated gasoline face significant losses, including damage to piston rings and engine blocks, fuel wastage, and damage to emission systems.
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