AbstractIn advanced fuel‐efficient engine oils containing molybdenum dialkyldithiocarbamate, Mo(dtc)2, as a friction‐reducing additive, the friction‐reducing capability is gradually depleted with mileage accumulation and is dependent on the presence of other additives, such as zinc dialkyldithiophosphate, Zn(dtp)2. Indeed, it has been shown that the loss of the friction‐reducing capability of Mo(dtc)2coincides with the depletion of Zn(dtp)2. The next generation of oils will specify a lower phosphorus content (e.g., 0.08% in ILSAC GF‐4 and even lower in the specification after GF‐4) to reduce the detrimental effects of phosphorus on catalyst systems. This will necessitate the use of less Zn(dtp)2, which could have an adverse effect on the retention of friction‐reducing capability.The aim of this study was to determine if the retention of friction‐reducing capability could be maintained or even increased at 0.05% phosphorus with newer molybdenum trinuclear, Mo3S7(dtc)4, additives. To facilitate the study, a modified laboratory‐based ageing test was developed which correlated with the loss of friction‐reducing capability in the Sequence VIB engine test. This ageing test was used to evaluate model blends of Mo3S7(dtc)4with Zn(dtp)2at 0.05% phosphorus and added antioxidants. The results indicate that it is possible to extend the retention of friction‐reducing capability. However, whether or not it can be extended beyond the current drain intervals is s