Lubricant additives have a strong influence on the tribological performance of internal combustion engine components, and it is currently one of the leading research driving forces within lubricant companies. However, the anti-friction and anti-wear additives work forming surface tribofilms may have their performance affected by ethanol or water contamination. As both ethanol and water are polar, they may compete on the surface with the additives, avoiding or delaying the additive tribofilm formation. In this work, the effect of ethanol and water on the performance of 4 different fully formulated SAE 0W-20 engine oils, differing only on the friction modifier (FM) additive technology employed, was investigated. In order to emulate fuel dilutions, three tests conditions were carried out for each engine oil: (i) fresh, (ii) in the presence of ethanol, and (iii) in the presence of ethanol and water. Friction and wear of actual piston ring and liner were evaluated in a reciprocating test designed to emulate actual thermomechanical conditions of both urban and highway car use. Amine and ester FM containing engine oils did not show a significant difference in friction in the fresh condition of the hot-running phase. However, with ethanol and water, amine and ester FM oils provided 30% and 20% friction reduction on the contact, respectively. In its fresh condition, molybdenum type FM-containing oil reduced the CoF (71%) drastically, and even worsening its performance with the ethanol and water dilutions, molybdenum-containing oil still kept a high level of CoF reduction when compared with the baseline oil and the other friction modifiers. The wear of the cylinder liner and piston ring was low, not being affected by the oil dilutions. Those results evidence that somehow the friction modifier performance, nowadays of utmost importance to achieve targets of fuel economy, is affected by the presence of ethanol and water in the lubricant, and the level of influence depends upon temperature and the formulation technology applied.