Modern passenger car motor oil (PCMO) and heavy duty diesel engine oil (HDDEO) are required to provide the critical functions of lubricating and protecting the performance of modern automotive engines. A lubricant must play a key role in cooling the engine, reducing friction and wear, maintaining engine energy efficiency, and improving fuel economy. In addition, increasing specification demands require these lubricants to be robust and durable, over extended mileage accumulation with longer drain intervals, throughout the life of the vehicle. In order to extend lubricant performance with extended mileage, the automotive and lubricant industry consortium requires that more challenging protocols be adopted for the fuel economy engine dynamometer test, ASTM D7589 (Sequence VIE). These test changes are directed in an effort to develop modern motor oils that both meet increasing fuel economy specifications and maintain performance durability. In order to develop friction modifier (FM) additives for modern PCMO with greater and durable fuel economy, it is useful to perform time-dependent tribological testing correlated with the fuel economy improvement (FEI) test conditions. In turn, FEI is measured by the Sequence VIE test under initial (FEI-1) and an aged (FEI-2) oil conditions. This test correlation is accomplished using Fourier transform infrared (FTIR) spectroscopy to match lubricant molecular-level changes during tribological testing to changes during the Sequence VIE test. The changes in the Sequence VIE test were designed to better measure fuel economy (FEI-1 and FEI-2) as a lubricant changes during extended real-world driving conditions.