Does E10 gasoline 'corrode' vehicles as many people fear?

VTV.vn - The cleaning and dehumidifying properties of alcohol in E10 fuel make car owners fear damage. However, degradation mostly occurs on non-metallic parts in very old motorcycles or cars.

The cleaning and dehumidifying properties of alcohol in E10 fuel make car owners fear damage. Photo: Hong Hanh

As news spread that RON 95 gasoline would gradually be replaced by E10 gasoline, the term "engine corrosion" suddenly became a haunting keyword for many drivers. Many vehicle owners in the transportation service industry, who depend on their vehicles for their livelihood, expressed particular concern. Vu Van Phuong, a driver in Ninh Binh , confided: "E10 gasoline would be good if it didn't pollute the environment, but I'm also afraid it will damage the engine and cost money to repair. Because drivers like us don't earn much." In hilly and mountainous terrain, customers also raised serious questions about the performance and potential damage to components from biofuels.

However, automotive experts quickly vindicated E10 gasoline, pointing out that the concept of "corrosion" is being misunderstood. Associate Professor Dr. Dam Hoang Phuc explained in detail: Ethanol in biofuel acts as a solvent with cleaning properties. Chemically, this solvent does not affect or corrode hard metal mechanical parts in the combustion chamber. Instead, ethanol mainly affects non-metallic materials such as gaskets, seals, and fuel lines made of rubber or plastic.

For older vehicles (cars manufactured before 2005, and motorcycles before 2000), the fuel lines and seals are not designed with alcohol-resistant materials. Continuous contact with 10% rubbing alcohol can cause the rubber to age, leading to fuel line leaks, carburetor blockages, or damage to the seals. This is the origin of the rumor that "E10 gasoline ruins cars." For vehicles without the "E" symbol on the fuel cap, which are usually more than 20 years old, checking and replacing aged rubber parts is mandatory.

Another chemical property of ethanol that has drawn the attention of engineers is its extremely strong ability to absorb moisture from the surrounding air. According to studies, if a user fills their vehicle with E10 gasoline but then stores it in a warehouse without using it for an extended period (usually over 3 months), the ethanol will silently absorb moisture. When the amount of water absorbed exceeds the solubility limit of the mixture, it will reach a critical point called "phase separation." At this point, the water and ethanol will separate into a layer that sinks to the bottom of the tank, while the mineral gasoline floats on top.

The consequences of this separation are extremely harmful. When starting the engine, it will directly draw in a water-like mixture into the combustion chamber instead of gasoline, causing the vehicle to have difficulty starting, run erratically, corrode the fuel tank, and damage the electronic fuel injection system. Therefore, experts strongly recommend that when using E10 gasoline, vehicles should be driven regularly and absolutely not left for too long with low fuel levels in the tank.

Following a trial period in Ho Chi Minh City, Hanoi , Da Nang, and Hai Phong starting August 1, 2025, many car and motorcycle owners have shared their experiences on automotive forums about trying E10 gasoline. They reported that their vehicles performed well and showed no concerns. However, owners of older vehicles should be cautious when choosing E10 gasoline, as it has been advised against use in older vehicles (manufactured before 2000) due to potential corrosion of rubber, plastic, and metal parts.

To reassure consumers, the Vietnam Automobile Manufacturers Association (VAMA) has committed to guaranteeing warranty coverage for customers who use the recommended fuel type. Warranty claims will only be voided if the damage is caused by using counterfeit, low-quality, or unverified fuel. Therefore, the key to using E10 fuel safely is not avoidance, but understanding your vehicle, adhering to regular maintenance schedules, and purchasing fuel from reputable gas stations.

Source: https://vtv.vn/xang-e10-co-an-mon-xe-nhu-nhieu-nguoi-lo-ngai-100260515102358627.htm