# Performance Assessment and Scooter Verification of Nano-Alumina Engine Oil
## 1 Introduction  
Enhancing material performance by using nanoparticles already has considerable achievements in the past decades. Nanoparticles (nano-additives) are added to the working fluid to form nanofluids which have been widely used to enhance the thermal conductivity, heat transfer performance, and tribological properties of the working fluid [1; 2; 3; 4; 5; 6]. In recent years, many researchers have added nanoparticles to oils in order to fabricate nano-oils that can improve the tribological properties of oil in order to enhance the operating efficiency and the life of machinery. The nano-additives in nano-oils comprise various metal oxide nanoparticles (Al\({}_{2}\)O\({}_{3}\), CuO, TiO\({}_{2}\), and ZnO) [7; 8; 9; 10; 11], metal nanoparticles (Cu, Ag) [12; 13; 14; 15], non-metal/metal oxide nanoparticles (graphite, boric acid, diamond, MWCNT/multi-walled carbon nanotubes) [16; 17; 13; 18], and hybrid nanoparticles (MWCNT/ZnO and SiO\({}_{2}\)-MWCNTs) [19; 20]. Most of the literature shows that nano-oils can reduce friction coefficients, power losses, wear, resistance, and can also improve thetribological performance of machinery. In addition, nano-oils had high thermal conductivity, enhancing heat dissipation caused by mechanical friction [9; 21]. Therefore, adding nanoparticles into oils to enhance their mechanical properties was expected. Many studies showed that the viscosity of nano-oils was increased with the concentration of nanoparticles [9; 11; 19; 20; 22]. However, the effect of nanoparticle concentration on the increasing viscosity of nano-oils is gradually reduced with increasing nano-oil temperature [9; 19]. Furthermore, the rheological properties of nano-oils exhibit Newtonian fluid behavior at low nanoparticle concentrations, while they show non-Newtonian fluid with shear thinning behavior at higher nanoparticle concentrations [22]. Operating performance evaluation of nano-oils in the actual operation of mechanical equipment has included refrigerators, vacuum pumps, internal combustion (IC) engines, gear rigs, bearings, etc. [PERSON] et al. [23] used a fullerene nano-oil in a refrigerator, and found that the electric power consumption was reduced by decreasing the friction coefficient and wear rate to the compressor. [PERSON] et al. [24] used an Al\({}_{2}\)O\({}_{3}\) nano-oil with various concentrations (0.1%, 0.2%, and 0.3 wt. %) in a direct-drive oil-sealed rotary vacuum pump. The optimal condition showed that the temperatures of cylinder, case surface, and discharge pipeline were reduced by 1.3%, 1.7%, and 3.8%, respectively. The performance of IC engines in terms of frictional power loss, fuel consumption, oil consumption, and harmful exhaust emissions is closely related to the friction force and wear between moving parts of the engine, such as the piston assembly, valve train, and bearings. Generally, frictional losses in IC engines vary between 17% and 19% of the total indicated horse power [4]. [PERSON] et al. [21] adopted graphene-based nano-oil in a four-stroke IC engine to investigate the coefficient of friction and the transfer rate of the engine. The results showed that the enhancement in thermal conductivity at 80 \({}^{\circ}\)C and the heat transfer rate of the engine were 23% and 70%, with a 21% reduction in the coefficient of friction of the piston rings by using a 0.01 wt. % graphene-based nano-oil compared to the base oil (API20W50 SN/CF). [PERSON] et al. [13] observed that a graphite and silver nano-oil enhanced load-carrying and anti-wear properties in the Forschungsgstelle fur Zahnrader und Getriebebau (FZG) gear rig test, and also reduced the electric power consumption by more than 3% compared to the base oil. [PERSON] et al. [25] investigated the influence of TiO\({}_{2}\) nano-oil on the load carrying capacity of a journal bearing. The results showed an increase in the load carrying capacity of a journal bearing using TiO\({}_{2}\) nano-oil as compared to the base oils without nanoparticle addition.