Abstract: There is also a growing need for internal combustion engines to improve fuel efficiency and reduce polluting emissions in the fight against global climate change. Efficient supercharging, antifriction coating, low viscosity lubricating oil and other energy saving technologies have appeared. The requirements of higher mechanical stress, higher speed and higher operating temperature in the new technology make it difficult for existing commercial internal combustion engine oil additives to meet. Nano additives have a broad application prospect in energy saving engine oils due to their high anti-wear and anti-friction effects. The co-effect mechanism between nano additives and commercial additives in engine oils is a key issue in developing the formula of nano additive engine oils. Quartz crystal microbalance (QCM-D) was used to study the synergistic adsorption behavior of oleylamine modified CeO₂ nanoparticles and commercial engine oil additives on metal surfaces, and the effect mechanism on anti-friction and anti-wear properties of CeO₂ nanoparticles. It was found that the formation of dense CeO₂ friction film on the surface of the friction pair by CeO₂ nanoparticles is the fundamental mechanism to achieve antifriction and anti-wear properties. When CeO₂ nanoparticles are mixed with commercial internal combustion engine oil additives, Dispersant (AD) interferes with the formation of CeO₂ friction film, resulting in its antifriction and antiwear properties lower than that of a single additive, showing an antagonistic effect. Other additives, such as Detergent (DE), Friction Modifier (FM), Antioxidant (AO) and Viscosity Index Improver (VII), can form friction films together with CeO₂ nanoparticles, making the anti-wear performance better than that of a single additive, showing a synergistic effect. Both CeO2 nanoparticles and the involved commercial additives are able to co-adsorb on metal surfaces. For Viscosity Index Improver (VII), Antioxidant (AO), Detergent (DE) and Dispersants (AD), the degree of co-adsorption of CeO₂ nanoparticles decreased with the increase of alkyl chain length in the additive. The polyisobutene (FIB) with molecular weight of 1300 in the Dispersant (AD) molecule greatly hindered the adsorption of CeO₂ nanoparticles, which could not be deposited on the surface of the friction pair to form a film, leading to a significant antagonistic effect. For the multi-layer viscoelastic adsorption of Friction Modifier (FM), the adsorption of CeO₂ nanoparticles on the metal surface increased significantly, resulting in the maximum adsorption mass. The wear resistance of CeO₂ nanoparticles combined with organic molecular additives is proportional to the adsorption mass of the adsorption layer. The combination with the Friction Modifier (FM) has the maximum adsorption mass and the smallest diameter of the grinding spot. The combination with Dispersant (AD) has the lowest adsorption quality, resulting in the grinding diameter of AD is larger than that of other additives. The friction film formed by the Detergent (DE) with inorganic nuclei and CeO₂ nanoparticles has stronger anti-wear ability than the single CeO₂ friction film.