Nowadays, the pollution of environment caused by used engine oil became one of the current global issues. One quart of oil can create a two-acre sized oil slick, and a gallon of oil can pollute a million gallons of fresh water. Some studies said that oil pollution caused 20 years for the environment to recover to its original condition [1]. This paper proposes a study on the quality of engine oil where the aim is to find the exact time to change the engine oil. The sample of used engine oil was taken from motorbike where the number of motorbike on the road was increased rapidly in town. The study was focused on the spectroscopy approaches where percentage of reflectance intensity was measured using MCS600 ZEISS Spectrometer. The data was summed up by a line graph and was verified using statistic approach called Student t-Test. The result shows that the more mileage of engine running will reduce reflectance intensity