As an alternative fuel with zero carbon emissions, ammonia has great potential for development in the shipping industry. Several initiatives and studies are underway to bring ammonia engines to the market soon. In this study, the tribological characteristics of lubricant used in ammonia fuel engines after contamination were investigated. The piston ring and cylinder liner were used as friction pairs, with cast iron as the base material and the piston rings coated with a chromium-based ceramic composite. The effect of ammonia was considered by introducing the combustion products of ammonia in an artificial engine oil modification process and employing these lubricants during the tribotests. The results show that the artificially altered oil will not only cause corrosion wear on the surface, but also destroy the anti-wear performance of the lubricant additives, resulting in increased surface wear. The outcomes of the work are anticipated to offer beneficial insights of lubricating oil uses in ammonia engines, particularly in scenarios where ammonia contamination poses a concern.