The growth of e-commerce platforms in the automotive sector is accompanied by the rampant circulation of counterfeit parts, so consumer trust is a crucial factor for business success. This study aims to comprehensively describe and analyze the marketing strategy of PartGenie, an original car spare parts e-commerce platform that serves the business to consumer (B2C) and business to business (B2B) segments, including segmentation, targeting, and positioning (STP) strategies, marketing mix implementation, as well as sales strategies and revenue projections. The research uses a descriptive qualitative approach with a case study design, sourced from primary data in the form of PartGenie business plan documents and secondary data from literature studies, analyzed through data reduction, data presentation, and conclusion drawn. The results show that PartGenie formulates segmentation based on demographic, geographical, and behavioral dimensions, with positioning that highlights the guarantee of product authenticity and platform convenience through the tagline "Trust in Every Drive". The marketing mix is applied differently, namely the 7P framework for the B2C segment and the NICE approach for the B2B segment, with the sales budget allocation dominated by the B2B segment up to eighty-nine percent of the total ten-year projection. Revenue projections show an exponential growth trend, especially since the region's expansion in the fifth year. It can be concluded that the integration of STP strategy, adaptive marketing mix, and measured sales planning is the main foundation of the business growth of trust-based automotive e-commerce platforms.