Most methods that are used to evaluate the performance degradation of engine oil require considerable amounts of the engine oil. Hence, novel techniques that require only small amounts of samples are needed. In this study, we investigated the feasibility of using the viscosity of and the intensity of light transmitted from a small amount of engine oil to evaluate the degradation of the oil. The viscosity was measured through repeated evaluations of the flow conditions using a fine capillary tube. The light intensity transmitted through the sample oil was measured using a light-emitting diode and photodiode. Using the two evaluation methods, we analyzed six oil samples that had undergone different durations of usage. Subsequently, the correlation between the durations and measured values was examined. The results indicated that the viscosity and light intensity decreased with increase in the duration of usage. From these results, we found that our viscosity and transmitted light intensity measurement methods could be used to evaluate the degradation of engine oil using small amounts of the oil. In addition, the transmitted light intensity can be used to estimate turbidity. Display omitted •Two methods were proposed to evaluate degradation in small volume oil samples.•One evaluation method is measuring viscosity, and another is measuring intensity of transmitted LED light.•Shell 15W40-DH2 engine oil was used as the evaluation sample after 58.3–1567.8 h of use in an engine.•Degradation could be evaluated by each method.•We clarified correlation between two proposed methods.