Engine oil is the vehicle's lifeblood: it lubricates, cools, and protects moving parts. Too often, oil changes follow fixed intervals, ignoring the lubricant's actual condition. A new study examined nine used oil samples from cars driving in city traffic, highways, hybrids, and diesel engines. Researchers measured kinematic viscosity and applied Fourier Transform Infrared (FTIR) spectroscopy to detect oxidation, nitration, sulfonation, fuel dilution, soot, and additive loss. Results show that even at similar mileage, oil aging differs greatly depending on driving style and engine type. In some cases, oil was changed too early, wasting resources; in others, it stayed too long, risking engine damage. FTIR uncovered subtle chemical changes, especially in oils exposed to biofuels or prolonged heat. Adding these tests to a conditionβbased maintenance strategy can cut waste, lower environmental impact, and extend engine life. A smarter approach benefits both the wallet and the planet.
FTIR analysis provides an infrared spectrum reflecting the molecular vibrations of chemical bonds in the oil. Oxidation bands (C=O pairs around 1740 cmβ»¹) increase with the formation of acids and peroxides, indicating thermal degradation. Nitration, typical of diesel engines, appears with peaks at 1550β1500 cmβ»¹ due to nitroβaromatic groups. Sulfonation, linked to sulfate additives, shows bands at 1150β1050 cmβ»¹. Fuel dilution is highlighted by an increased CβH band at 2950β2850 cmβ»¹, while soot generates a sp² carbon signal around 1600 cmβ»¹. Loss of antiβwear additives such as zinc dialkyldithiophosphate (ZDDP) results in decreased bands at 1240 cmβ»¹ (PβO) and 600 cmβ»¹ (ZnβS). Simultaneously, kinematic viscosity measured at 40β―°C and 100β―°C provides a flow index: a rising viscosity index signals oxidation aging, whereas a drop may stem from fuel dilution. Integrating these parameters enables building a predictive model using machineβlearning algorithms that correlate spectroscopic and viscosity data with operating conditions (temperature, load, fuel type). This model can generate dynamic oilβchange thresholds, optimizing timing based on the lubricantβs actual chemical state, thereby reducing waste oil consumption by roughly 30β40β―% compared to traditional schedules.
