It has been long established fact that fuel economy is a key driving force of low viscosity gasoline engine oil research and development considered by the original equipment manufacturers (OEMs) and lubricant companies. The development of low viscosity gasoline engine oils should not only focus on fuel economy improvement, but also on the low speed pre-ignition (LSPI) prevention property. In previous LSPI prevention literatures, the necessity of applying Ca/Mg-based detergents system in the engine oil formulations was proposed. In this paper, we adopted a specific Group III base oil containing Ca-salicylate detergent, borated dispersant, Mo-DTC in the formulation and investigated the various effects of Mg-salicylate and Mg-sulfonate on the performance of engine oil. It was found that Mg-sulfonate showed a significant detrimental impact on silicone rubber compatibility while the influence from Mg-salicylate remains acceptable. The newly developed 0W-16 engine oil in this paper showed 1.0% fuel economy improvement (FEI) compared to typical GF-5 0W-20 engine oil. In addition, adequate fuel economy retention property of the 0W-16 engine oil was demonstrated in the ageing process. This newly developed engine oil also passed LSPI test and all of the bench and engine tests required by GF-5, which implied that this oil could provide good protection for engines.